How do I make mashed potato ahead of time?

The reason mash gets a reputation as a last-minute job is that thin mash reheats badly and everyone reheats it too fast in a dry pan. Extra fat and gentle heat solve both problems.

Step by step

1. Make the mash slightly richer than you would to serve straight away.Fat protects the starch from drying and from turning gluey when reworked. A little more butter, and warm whole milk or cream rather than the minimum. It will not taste heavy once it has been through a hold or a reheat.
2. To hold for up to two hours, use a bain-marie.Put the mash in a heatproof bowl over a pan of water held just below a simmer, cover with a lid or foil, and stir occasionally. Gentle indirect heat means it will not catch or dry. This is what restaurant kitchens do and it is far better than a low oven.
3. To hold overnight, cool fast and cover the surface.Spread it into a shallow dish so it cools quickly, then press cling film or buttered greaseproof directly onto the surface before refrigerating. Direct contact stops a skin forming and stops it drying at the edges. Keeps three days.
4. Reheat covered, in the oven or the microwave, with extra liquid.Oven: dot with butter, add a splash of milk, cover tightly with foil, 160°C for 25–35 minutes, then stir. Microwave: cover, medium power, stir every couple of minutes. Both need stirring at least once, because the outside heats first.
5. Freeze it flat, in the portions you will use.Bag it and flatten to about 2 cm so it freezes and thaws quickly, or freeze scoops on a tray and bag them. Up to three months. Freezing works because the fat protects the starch structure; low-fat mash freezes noticeably worse.
6. Reheat from frozen rather than thawing.Covered dish, 180°C, with a splash of milk, until hot right through — an hour or more for a large block. Thawed mash weeps and needs beating back together; frozen straight to hot does not.
7. Beat in a knob of butter at the end.Whatever route you took, a fresh piece of butter stirred through just before serving restores the gloss and the taste of freshly made mash. This is the whole trick.

Tips

• A ricer or mouli gives mash that reheats better than a masher, because there are no lumps to go grainy and no risk of the over-working that turns starch gluey.
• Mash topped on a pie — cottage, shepherd's, fish — can simply be assembled cold and baked from cold, which is the easiest ahead route of all.
• Do not use a food processor or stick blender at any stage. It ruptures the starch granules and gives you wallpaper paste, and reheating makes that worse.

Common mistakes

• Reheating uncovered in a saucepan on direct heat — It catches on the base and dries at the surface. Covered and indirect, always.
• Holding it in a warm oven for hours — Dry oven heat crusts the top and dries the whole thing. A covered bowl over water is the right tool.
• Making it deliberately lean to reheat — Fat is what makes mash survive holding, chilling and freezing. Lean mash goes gluey and grey.

Questions people ask