How to make the crispiest, crunchiest roast potatoes you've ever had

How to make the crispiest, crunchiest roast potatoes you've ever had

If you love a roast spud with all those golden-brown crisp-crunchy edges, then you’ll know just how disappointing it is to put a tray of potatoes in the oven, full of promise and expectation, and then, when they are done, take out soft, pale starchy chunks that might be roasted potato but aren’t ROAST POTATOES.

So what’s the secret? There are, in fact, five key things, none of them hard, that you can do to give you those golden-crusted ‘taters of your dreams.

Pick the right potato

You want a starchy (also often called floury) potato for this job. Waxy potatoes are good for salads and such, but for a crisp roast potato, look for starchy varieties or versatile allrounders, such as Sebago (used in those crunchy rosemary roast potatoes below), Coliban and King Edward and Desiree.

How to make the crispiest, crunchiest roast potatoes you've ever had

Best ever rosemary roast potatoes

Boil them before roasting

Yes, boiling adds to the time taken to make your ‘taters – but it’s worth it!

“Simply toss a potato coated with a bit of oil in the oven, and what you end up with is a potato with a paper-thin sheath of crispness around its exterior that very rapidly softens and turns leathery as internal moisture seeps through it,” says Kenji López-Alt, who has been serving up his science-meets-home-kitchen column, The Food Lab, for the popular Serious Eats website since 2008. “So, what makes a potato crisp? The answer is building up a dehydrated layer of gelatinised starch on the exterior of the spud, much like when you fry a French fry. To do this, you’ve got to parcook them, allowing their starches to soften and expand, and then recrystallise by cooling them a bit,” he explains in his recipe for super-crisp roasted potatoes, shared with us from his book, The Food Lab: Better Home Cooking Through Science.

“Our secondary goal is to increase their surface area. Craggy, uneven surfaces crisp up a lot better than smooth ones … By boiling your potatoes before you roast them, not only do you ensure that their outer layers of starch are properly gelatinised, you also soften their exteriors enough that they get a bit battered and bruised when you toss them around with oil before roasting them.”

These crispy-edged roast spuds are a potato lover's dream.

Make more edges to make more crunch

Here’s where the experts diverge a little. Some recipes say to drain the potatoes after boiling, then shake them around in the pan you cooked them in, to bash up the edges. It does work. Take a look at these crunchy numbers from Tony Singh, served with Cyrus Todiwala's honey-roasted chicken (the pair call them "outstanding roasties" and you can see why!):

How to make the crispiest, crunchiest roast potatoes you've ever had

Duck fat renders the skin of a roast chicken a deep, golden brown

But Tom Kerridge, a chef who clearly knows his way about a roast spud, having garnered two Michelin stars for his pub food, does it another way.

“I know how you cook your roast potatoes at home, you drain all the water off and then you keep the lid on and you give it a good shake. Stop doing that,” he says in the Sunday Lunch episode of Tom Kerridge's Proper Pub Food (starting June 8 on SBS Food; catch double episodes from 7.30pm). Instead he uses a slotted spoon to move the potato pieces to a cake cooling rack (set over a tray to catch any water). “By allowing these potatoes to now steam on a cake rack they dry out, so the overcooked potato on the outside goes fluffy. The hot oil can then get inside the spuds and make them crispy,” he explains.

How to make the crispiest, crunchiest roast potatoes you've ever had

Kerridge has a couple of other good tips for making what he promises will be “some of the most crispy wonderful roast potatoes you’ll ever have” (get the recipe here). Use unwashed potatoes - “If you buy dirty potatoes you know that they’re unwashed and they’ve not taken on any extra water; if they take on any extra water it’s harder to make them crispy”; and cut your potatoes into pieces about the same size, so they cook evenly.

Heston Blumenthal uses a similar drying technique in his roast potato recipe, draining the boiled potatoes carefully and then leaving them to cool in a colander.

Go for good oil

“Don't scrimp on the amount of oil added to the pan – it is the fat gathering in the cracks that makes the potatoes so crispy,” says Blumenthal.

Wondering what oil is best?

“People often tout the awesomeness of duck fat with potatoes, and for good reason: it tastes awesome. Duck fat has a distinct richness and aroma that gets absorbed very easily into the surface of a spud,” says López-Alt.

But if you haven’t got duck oil to hand, don’t worry. This is one part of the supreme spud process where there’s plenty of variation in what the experts recommend. Use what you’ve got, try different options, decide what you like best.

“I use veg oil and not duck fat because veg oil is pretty much flavourless, it’s all about the potato, not about the fat,” says Kerridge. “Olive oil works really well or you can use goose fat or beef dripping, but they will give a different flavour,” says Blumenthal. López-Alt also likes turkey fat or chicken fat collected from roasted birds, bacon fat and rendered lard. Olive oil will also do the job well, he says, although he reckons animal fats give just a little bit more crispiness.

Don’t rush the roast

One last tip – do turn your ‘taters during the roast, so you get all the edges crisp and brown, but don’t force it.

“The key is to make sure you let the undersides crisp up completely before you even attempt to lift or flip them. If the potatoes don’t come off relatively easily, you run the risk of breaking off the tops, leaving the crisp bottoms cemented to the bottom of the pan,” says López-Alt, in one of the many explanatory notes on his very thorough recipes.

This tip is worth embracing, because who wants to leave those excellent crispy bits stuck in the roasting tray, instead on your plate?

Bottom line: buy the right spud, boil them before baking, try all the tricks for maximising surface area and the potato's ability to soak up oil, and turn them carefully during roasting. And make more than you think you'll want!