Onion, Prosciutto and Taleggio Tart

375g Puff Pastry
3 Tbsp Olive Oil
3 Medium Onions, finely Sliced
1 Tsp Fresh Lemon Thyme Leaves
Salt and Pepper
85g Finely Sliced Prosciutto
150g Taleggio Cheese

1) Preheat oven to 220c/400f/Gas Mark 7.
2) Roll out pastry to 35cm 8 25cm rectangle, to about the thickness of a 50p coin. Slip onto a backing tray and trim and score a border 2cm inside the edge. Prick the inner rectangle with a fork. Chill for 30 mins.
3) Heat oil in a frying pan over a medium-high heat and add the onions. As soon as they collapse, reduce the heat and fry for about 15 minutes or until soft. Add the thyme and season to taste.
4) Once cool, spread the mixture over the base, taking care not to spread it into the border. Roughly cut the Prosciutto into 5cm squares and scatter over the onions. Remove the rind and slice the taleggio into similar sized squares. Sprinkle over the onions.
5) Bake the tart in the centre of the oven for 10 minutes, then reduce the temperature to 200/400/Gas 6 and cook for a further 5 minutes or until the pastry is crisp and the chesse golden and bubbling.

Variations
Asparagus, Onion and Taleggio -Steam the asparagus for 3-5 minutes until al dente and use instead of (or with) the prosciutto.