Preheat the oven to 375°F / 190°C / Gas Mark 5, no fan.
Place the puff pastry sheet on a lightly floured piece of parchment paper, roll it out crosswise (only the shorter edges so that the dough is wider).
Cut it into 15 squares. Using a small knife, score (do not cut all the way through the pastry) the edges of each square to create a border.
Spread a teaspoon of pizza sauce in the middle of each square (don't add too much so that the pastry is not soggy).
Top with sliced ham, salami, mushrooms, and olives.
Bake for 10 minutes, then sprinkle the cheese on top, and bake for 15 more minutes, or until the pastry is puffed and golden.
Spread some basil pesto onto the pastries.