Milk

Warm it gently in a heavy-based pan over low to medium heat, stirring often and scraping the bottom. Take it off the heat as soon as it steams; a sudden boil can make it foam over and leave a burnt taste.

Cold milk froths more easily. With a steam wand, keep the tip just under the surface until the milk expands, then lower it to swirl; aim for about 60–65 °C and tap the jug to break up large bubbles.

Keep it covered in the fridge at 4 °C or colder, ideally on a shelf rather than in the door, where temperatures fluctuate. Follow the use-by date and discard it if it smells sour or has become lumpy.

Yes. Freeze it in a sealed, freezer-safe container with room for expansion, and thaw it in the fridge. It may separate after thawing, so shake it well; the texture is usually better for cooking than for drinking.

Acid and high heat can make milk proteins clump. Lower the heat, stir constantly, and add the milk gradually; for tomato sauces, a little cream or a flour-thickened white sauce is less likely to split.

Unsweetened soya drink is a close swap in equal amounts and browns well. Oat drink also works, though it can make pancakes slightly sweeter; avoid flavoured or sweetened versions for savoury batters.

Milk gives porridge and mashed potato a soft, creamy texture, and it is the base for white sauce used in lasagne and macaroni cheese. Warm it before adding it to mashed potato so the potatoes stay hot.

You can, but warm milk blends into the roux more smoothly and reduces the chance of lumps. Whisk it in a little at a time, then simmer for a few minutes until the sauce thickens.