Vegetable lasagne rests on the worktop before I cut it

Vegetable lasagne is the dish I make when the vegetable drawer is full of odds and ends and the week has been long. It takes a while, it fills the oven, and the whole kitchen smells of tomato, garlic and browning cheese. For a long time it also had a sad ending: I would carry the hot dish to the table, cut into it, and watch the layers slide apart into a pink puddle. The fix turned out to be the easiest step of all. When the lasagne comes out of the oven, it rests on the worktop for fifteen to twenty minutes before I cut it.

I start with the vegetables. For four to six of us I chop 2 courgettes, 1 red pepper, 1 aubergine and 1 onion into small pieces, toss them with olive oil and roast them on a big tray at 200°C (180°C fan, gas 6) for about 25 minutes, until soft and browned at the edges. Roasting drives off water, and water is the enemy of a lasagne that holds its shape. Then I stir the vegetables into a sauce of 2 tins of chopped tomatoes simmered with 2 cloves of garlic, a spoon of tomato purée and dried oregano until thick. If you can drag a spoon through it and see the pan, it is ready.

The white sauce is the same one I make for macaroni cheese: 50 g of butter, 50 g of plain flour and 600 ml of milk, whisked over a medium hob until thick, then a good handful of grated Cheddar and a little nutmeg. I make it slightly thicker than for pasta, because it has to hold layers.

In a deep ovenproof dish I build it in order: a thin layer of the tomato and vegetables, then dried lasagne sheets, then more vegetables, then a few spoons of white sauce, and again, finishing with sheets covered in the rest of the white sauce and a handful of cheese. It bakes at 190°C (170°C fan, gas 5) for about 40 minutes, until the sheets are tender when I push a knife in, the top is golden and it bubbles at the edges.

Then I make myself wait. I set the dish on a board on the worktop, lay the oven gloves next to it and lay the table. In those fifteen or twenty minutes the sauces thicken and settle and the pasta finishes soaking up the juices. When I cut it after that, the knife goes down through clean layers, and the square lifts out on the slice still looking like a lasagne. It is still properly hot inside, so nobody is eating a cold supper.

I always make more than we need, because lasagne is better the next day. The Food Standards Agency advises cooling leftovers and putting them in the fridge within two hours, eating them within two days, reheating only once until steaming hot, and even mentions that dishes like lasagne heat more evenly in smaller portions. So I cut the cold leftovers into single squares and reheat them one at a time until steaming hot right through. Contains milk and wheat (gluten).

It is a calm kind of dish once it is in the oven, and it forgives a lot: a different mix of vegetables, a little less cheese, sheets from the back of the cupboard. And the rest at the end costs nothing; it is just twenty minutes of laying the table and pouring water while the layers sort themselves out.

So next time you take a lasagne out of the oven, put it down and step away. What do you do in those twenty minutes while it rests?