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How to cook perfect spuds


Heston Blumenthal

Heston Blumenthal helps us mash, roast and deep-fry our way to heaven, with knowledge that's far from skin deep.

Heston's way ... Roast potatoes with a crisp, glass-like crust (recipe below).

Heston's way ... Roast potatoes with a crisp, glass-like crust (recipe below). Photo: Angela Moore

You might think that giving background information on how to cook potatoes is unnecessary. After all, a potato's a potato, and even the most inexperienced cook has a pretty good idea of how to prepare it.

And yet it's surprisingly easy to end up with gluey mash, limp chips or leathery roast potatoes. It turns out that the humble potato is quite a complex structure.

If you want to get the best out of it, it's worth understanding that structure, and how best to handle it to create lovely, silky mash, or chips and roast potatoes with a wonderfully crunchy exterior and a soft, fluffy interior. First of all, a potato isn't just a potato.

Heston Blumenthal ... how to cook the perfect potato.

Heston Blumenthal ... how to cook the perfect potato.

Behind that name lie hundreds of varieties, among them anya, charlotte, desiree, king edward, marfona, maris piper and pink fir apple*. Each of these has a slightly different structure that responds slightly differently to cooking. Choosing the right potato will make a difference to the end result.

Although it looks like a solid knobbly lump, about three-quarters of a potato is water. The rest is known as ''dry matter'', principally starch. It's the dry matter that gives a potato its flavour, and managing the dry matter is central to cooking good mash, chips and roast potatoes.

Growing conditions have such an influence on dry matter that the amount in a single variety can vary virtually from field to field, depending on the temperature, rainfall and drainage. It's not an exact science. You can cook a particular variety perfectly one day, then find it responds badly the next.

In general, floury potatoes, such as anya, king edward and maris piper, have more dry matter, while the waxy charlotte and marfona have less. You might therefore think it's a simple case of going for a potato with high dry matter, after all, maximising flavour is what it's all about. But there's more to it.

All starch granules are made up of a proportion of two molecules - amylose and amylopectin - which respond to heat and cooking in different ways. Amylose tends to form a strong, tightly knitted gel; amylopectin coheres more loosely.

I'm looking forward to the day when bags of potatoes come with information about dry-matter percentages and amylose-amylopectin ratios printed on them - it will really help cooks find the perfect potato. For chips or roast potatoes, you're looking for a variety that's high in dry matter, with a reasonable proportion of amylose to help keep the shape. For mash, too much amylose is best avoided as it can lead to a gummy consistency.

When cooking roast potatoes (and chips), I want an interior that's soft and fluffy, with a crisp, almost glass-like, crust. Although you're working towards these aims simultaneously, it's helpful to think of them as separate tasks, each requiring a specific process.

For that soft interior, it's best to use a type of potato with a high dry-matter content and simmer carefully until it's almost falling apart. Be brave about this because the outer crumbliness is the key to a good final crust, as well as a soft inside.

For the crust to be properly crunchy, the fat needs to pool and collect in little pockets that harden and crisp up. If you've simmered the potato until it's only just holding together, lots of cracks and fissures will have developed in the surface - perfect places for the fat to collect. (Fat will penetrate the potato only where there is a crack.) To give the fat as many places as possible to catch and harden, it's best to use large potatoes cut into quarters or, better still, eighths, so there are plenty of pointy edges where fat will collect.

First rinse the cut potatoes in water for five minutes or so: this washes off surface starch, which would make the cooked potato less fluffy and crisp. For roast potatoes, the pieces are then cooked in unsalted water - salt can occasionally make the crust a little chewy, so it's safer not to add any. Potatoes with high dry matter fall apart more easily than those with a lower dry-matter content, so you'll need to keep an eye on them while simmering. Appearances can be deceptive: a potato will often look as though it's firm right up to the moment where it falls apart, so you need to periodically remove one and check it.

When they're ready, the potatoes need to be lifted very gently out of the water with a slotted spoon into a colander (don't just tip them, which will almost certainly turn them to mush). Leave them to steam, which will ensure moisture evaporates (it might otherwise make the crust soft or soggy) and the potatoes firm up and are not too fragile to work with.

Once cool, the potatoes are ready for the roasting tray, and all that careful preparation should guarantee a great roast potato. Make sure you hold on to any bits of potato that have broken off and put them in the roasting tray too. They will turn into lovely little nuggets of crispiness.

Since, for me, chips have to have a fluffy interior similar to a roast potato's, the first stages of cooking them are much the same: rinsing off surface starch, simmering the cut pieces until they're very soft but just holding together, with lots of little cracks in the surface. This requires careful and regular checks with a slotted spoon. By the time the chips are ready, they'll be fairly fragile and have to be handled delicately, although they'll become slightly more robust once they have cooled.

As far as crisp chips go, moisture is the enemy. When I discovered this, I went to extraordinary lengths to try to combat the problem - oven-drying chips or even individually pin-pricking them to get rid of excess moisture. The most practical solution for the home cook, however, is a concerted drying-out process, drawing on the air-drying abilities of the freezer, both before and after the first session in the deep-fryer.

Double frying is the other key to great chips. The purpose of the first session in the fryer, at a gentler temperature, is to make any starch left in the surface cells dissolve and combine to create a rigid outer layer that can withstand the higher temperature of the final frying, which will colour the chips golden. Skipping this can undo all the trouble you've taken to dry out the potatoes and drive off moisture.

A single frying at a high temperature leads to a thin crust that can easily be rendered soggy by whatever moisture remains in the chip's interior. Although this first, low-temperature frying might seem a time-consuming process, once the chips have had it, they can be stored in the fridge for up to three days before their second, high-temperature frying.

As for mashed potato, you can, of course, simply boil and mash some spuds. It might be a bit lumpy, but it will work well enough to go with a couple of bangers. However, there are times when a dish calls for something more refined, and no less than pommes purees will do.

Creating a perfect, velvety texture requires a little more work, but it's worth it. The end result will be a real taste of luxury.

The success of pommes purees is largely dependent on managing the starch. Cooking has to break down the cell walls of potato without damaging the starch granules. If they're overcooked, the granules leak starch, turning the mash into a sticky, wallpaper-paste-like mass.

The key to preventing this is an initial 30-minute simmer at precisely 72C, which alters a potato's structure so it responds well to the subsequent boiling and mashing. Cooking the potatoes at this temperature starts a process called ''gelatinisation'', in which the starch granules absorb water and swell to become a gel. (The process starts at 45C and stops at about 75C, hence the need for precision.) It also strengthens the potato's cell walls, so they're less likely to disintegrate.

After this first simmer, it's essential to cool the potatoes completely because this causes the starch molecules to firm up (an activity known as ''starch retrogradation''). At this stage, the potatoes will look uncooked but don't worry, they're now perfectly prepared for the final stage of cooking, which is simply softening by boiling in water as normal.

Using this two-stage cooking technique prepares potatoes perfectly for mashing. Nonetheless, it's vital that this final stage is done carefully so as not to undo all your work. Mashing is an invasive process and if it's done too aggressively, there's a risk that, instead of neatly separating the potato, the swollen starch granules will burst, leaking starch into the mash.

Using a food processor to mash will just produce a gummy pulp, and even a masher is likely to cause some damage. For the smoothest pommes purees, it's better to use a food mill or potato ricer, which grinds the potato gently, rather than blitzing or squashing it, so the starch granules remain intact.

RECIPE: Heston Blumenthal's roast potatoes

Extract from Heston Blumenthal at Home.

* Most of these are not available in Australia. Floury Australian potatoes include: king edward, sebago and dutch cream. nicola and kipfler are waxy potatoes. Purple congo has a dry texture. Nashdale Fruit Company sells pink fir, charlotte (waxy) and king edward potatoes at Glenbrook, Castle Hill and Penrith farmers' markets.



  • So much for potatoes!

    Date and time
    April 17, 2012, 12:34PM
    • Any cooking process that requires an artical of this length is too long.

      Date and time
      April 17, 2012, 4:39PM
  • THE best way to mash (in my opinion) is to use a fork. A regular table fork. First step is to break down lumps by crushing them against the side/bottom of the bowl; final step is to beat energetically until the desired consistency is reached. I prefer butter to cream, and just a dash of milk if the mix seems too dry.

    North Sydney
    Date and time
    April 17, 2012, 12:39PM
    • Agreed - I use the humble fork and mash them against the sides and then "whip" the mash with the fork using butter/marg and milk. Better and more consistant than the standard potato masher IMO.

      Date and time
      April 17, 2012, 2:25PM
    • Yay, 2 other people who stick with the old fashioned way! The fork is the only way to go, and so much easier to clean than those mashers or ricers! I have gone away from using milk as it seems to make the mash a little bland in flavor. Boiling a clove of garlic in the water with the potatoes as well can make the best garlic mash, or adding parmesan to the mash along with the butter makes the perfect mash to go with your lamb shanks on a cold winters night.

      Date and time
      April 17, 2012, 3:29PM
    • I use a metal whisk to make mash potato.

      Date and time
      April 17, 2012, 4:24PM
    • +1 on the whisk. I use a powered one, and the consistency is closer to whipped cream. That way you can serve up an impressive mountain of it and people can actually finish it.

      Caulfield South
      Date and time
      April 17, 2012, 5:34PM
  • None of the classic potatoes mentioned here (eg king edwards, desiree even) are routinely sold in supermarkets anymore. Instead they try to force us to buy tasteless rubbish potatoes like 'golden delight.' Presumably these have some cost-saving characterisic for growers and storers, maybe they are disease resistant or something. The potatoes that Colesworths try to push on us ('red rascal' ect) are appalling travesties of this noble tuber.

    Date and time
    April 17, 2012, 12:50PM
    • That is why you don't buy fresh food from the supermarkets.
      My green grocer sells organic dutch creams (my favourite) desiree and kipfler weekly as well as selling the basic brushed and & sebago
      Always worth shopping at the green grocer

      Messy Diner
      All over the table
      Date and time
      April 17, 2012, 1:14PM
    • I need my glasses. I originally read that as 'transvestites'.

      Billygoat Gruff
      Date and time
      April 17, 2012, 1:31PM

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