Preheat the oven to fan-assisted 170C / 190C / 375F / gas 5 and line a baking tray.
Heat the oil in a frying pan and fry the bacon pieces until they are done and set aside.
Lay the puff pastry sheet on the baking tray and score a 1cm border round the edge taking care not to cut all the way through.
Spread on the pesto, before toping with the bacon, tomatoes and finally the mozzarella.
Bake for 20 mins, until the pasty is puffed round the edges and golden.
Serve with extra pesto drizzled and rocket leaves on top.
Serves 6 with a side salad.