Onion and Cheese Tart

Ingredients
6 Onions, sweet white or red onions, or leeks
4 tbsp butter, approximate quantity
250g puff pasty
100g Taleggio cheese, fontina, or similar semi-soft cheese
2 sprigs Thyme, or enough leaves to make a little pile in your palm

Method
1. Peel the onions; cut them in half from stem to root, then into thick segments. Put them into a shallow pan with the butter and leave over a moderate to low heat until they are soft. Let them take their time. They need to be translucent, golden, and sticky. This only comes with slow cooking and it is pointless to try to hurry it. The actual timing will depend on the type of onion (some contain more water than others), but you can expect them to take a good 30 minutes.

3. Set the oven at 225°C/gas 7. If you are using a sheet of ready-rolled pastry, simply unroll it onto a lightly floured baking sheet. If you are using a block of pastry, roll it out into a rectangle (or square or round) no thicker than a coin. Score a border 2cm in from each edge and prick all over with a fork.

4. Tip the onions onto the pastry, pushing them almost, but not quite, to the border. Brush the rim with some of the onion butter. Slice the cheese thinly, then break it up into small pieces, tucking it in among the onions. Scatter the thyme over. Bake until the pastry is golden and puffed and the onions are browning-- 15-20 minutes.