Method

1. Set the oven to 200°C/gas 6. Melt half of the butter in a saucepan and add 1 tablespoon of the olive oil. Add the onions, pancetta and garlic and fry for 3-4 minutes or so, until golden.

2. Add the potatoes and cook together for a minute or so. Transfer to a bowl.

3. In the same frying pan, add the remaining butter and olive oil; then add the mushrooms. Fry for 1 minute and then return the onion mixture back to the pan.

4. Mix the thyme and cream in a bowl and season with salt and freshly ground black pepper. Pour in the white wine.

5. Stir in the potatoes and then transfer everything to an ovenproof dish. Lay the Reblochon evenly over the top and then bake for 20 minutes until golden brown and bubbling.