- 2 kg potatoes, choose a type such as agria
- 1 large onion, chopped
- 75g unsalted butter
- 200ml milk, heated
Peel potatoes and cut into large chunks. Put potatoes in a large saucepan, cover with cold water and salt lightly. Bring to the boil, lower the heat, then cook gently until tender. Drain potatoes, wipe out pan and return potatoes to it, then set the pan back over the heat for about 30 seconds. This drives off excess water.
Put onion in a small pan with the butter, cover pan with a lid and cook very gently for about 12 minutes until very soft but not coloured. (The onion could be cooked ahead, making one less last-minute thing to attend to.)
Pass the potatoes through a mouli-legumes, or mash with a hand-masher (Tupperware make an excellent hand-masher). Season with about 1 teaspoon of salt add onion, scraping in all the buttery juices, then beat in hot milk. Give potato puree a good whip with a wooden spoon, and check for seasoning (it should taste delicious; if it tastes a bit flat or boring, whip in more salt).
Keep potato puree hot by transferring it to a heavy china bowl - choose a deep bowl which will contain the heat more than a wide shallow bowl and heat it first by filling it with boiling water, then drying. Cover the bowl with a china plate and put the bowl on the hob top to keep warm. The puree will stay warm for up to 15 minutes by this method, giving you time to finish off other dishes of the meal.