Step 1

Preheat the oven to 400F

Step 2

Unfold the puff pastry sheet onto a piece of parchment paper cut to fit a baking sheet. Lightly dust with flour and roll out just a little bit longer and wider, to about 10x13, more or less.

Step 3

With the tip of a sharp knife score around the edge of the sheet, about 1/2 in from the edge, to form a frame.

Step 4

Spread or crumble the Boursin cheese evenly across the pastry, leaving the edge free.

Step 5

Top the cheese with the slices mushrooms, overlapping them to cover the whole surface.

Step 6

Sprinkle with salt and pepper, and brush lightly with olive oil.

Step 7

Bake for about 30 minutes, or until the tart is crisp and golden.