Waxy versus floury, and the techniques behind genuinely crisp roast potatoes and silky mash.
Section 01
Waxy or floury — choose first
Potatoes divide by starch content, and the choice determines what is possible. Floury (starchy) potatoes like russet and Maris Piper have low moisture and high starch: they go fluffy, absorb fat, and fall apart. Waxy potatoes like new potatoes, charlotte, and fingerlings hold their shape and stay dense.
All-rounders like Yukon Gold sit in the middle and are the sensible default if you only keep one kind.
Matching potato to method
Roasting
Floury
Fluffy interior, crisp exterior
Mashing
Floury
Absorbs butter, goes light
Chips / fries
Floury
Dry interior fries better
Boiling / salads
Waxy
Holds shape, does not crumble
Gratin
Waxy or all-rounder
Slices stay intact
Soup
Floury
Breaks down and thickens
Section 02
Genuinely crisp roast potatoes
Peel and cut floury potatoes into large, uneven chunks. The irregular faces become the crisp bits.
Boil in well-salted water until the edges are just starting to soften — about 8 minutes past the boil.
Drain thoroughly and let them steam dry in the colander for a few minutes.
Shake the colander hard to rough up the surfaces into a starchy fuzz. This is the step everyone skips and it matters most.
Add to a tray of hot fat — duck fat, beef dripping, or oil — already heated in the oven at 220 °C.
Roast 45–60 minutes, turning once or twice, until deep golden.
Chef's tip
The roughed-up starchy surface is what crisps. A smooth potato going into hot fat will never get there.
Section 03
Mashed potatoes
Start floury potatoes in cold salted water so they cook evenly from outside to center, and cook them whole or in large pieces so they absorb less water. Drain and let them steam dry before mashing.
Use a ricer or food mill. A masher gives a rustic result and a food processor is a disaster — the blades rupture the starch granules and produce something closer to wallpaper paste than to mash.
Warm the butter and cream before adding. Cold dairy seizes the starch and makes mash gluey.
Section 04
Fries and chips
·
Double-frying is essential: once at 160 °C to cook through, then again at 190 °C to crisp.
·
Rinse cut potatoes to remove surface starch, then dry them completely.
·
Rest between fries — at least 30 minutes, or refrigerate for hours. The pause lets the surface dry.
·
A short boil in salted vinegared water before frying gives the crispest results of all, because the vinegar limits pectin breakdown while the surface roughens.
Store potatoes cool, dark, and dry, but not in the fridge. Below about 4 °C the starch converts to sugar, which makes them unpleasantly sweet and causes them to brown far too fast when fried.
Keep them away from onions — onions release gases that accelerate sprouting. Green patches indicate solanine and should be cut away generously; a heavily greened or sprouting potato should be discarded.
·
Roughing up parboiled potatoes in the colander is the single highest-impact roast potato technique.
·
Preheat the fat in the tray. Cold fat makes greasy potatoes.
·
Never use a food processor for mash.
·
Salt the boiling water heavily. Potatoes are bland and need seasoning from within.
Avoid these
Common mistakes
Using waxy potatoes for roasting or mashing and wondering why they are dense.
Skipping the parboil and the roughing-up step.
Adding cold butter and milk to hot potatoes.
Mashing in a food processor and creating glue.
Storing potatoes in the fridge.
Frying only once and getting limp fries.
Get your hands dirty
Practice exercises
Roast two batches: one parboiled and roughed up, one raw. The difference is the whole lesson.
Mash the same potatoes with a ricer and with a masher. Compare texture.
Double-fry chips with a proper rest between stages, then compare to single-fried.
1. Why should you rough up parboiled potatoes before roasting?
The starchy fuzz created is what crisps in hot fat
To season them more evenly
2. Why does a food processor ruin mashed potatoes?
The blades rupture starch granules, releasing starch into glue
It incorporates too much air
3. Why should raw potatoes not be refrigerated?
Cold converts starch to sugar, making them sweet and prone to over-browning
If you remember nothing else
Key takeaways
Takeaways
Floury for fluffy, waxy for structure.
Parboil, dry, rough up, then hot fat — the crisp roast potato formula.
Warm dairy into dry potatoes for silky mash; never use a processor.
Never refrigerate raw potatoes.
Cook it
Practice on these recipes
Duck Fat Roast Potatoes
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Crème Fraîche Smashed Potatoes
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Schmaltz Roast Potatoes & Onions
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Roasted Sweet Potatoes
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The On The Fly Kitchen · Updated 2026-07-29