Place a puff pastry with baking paper on a baking tray. Prick the base several times. Mix the pan-fried vegetables and onion mixture and spread on the pastry. Leave the edge of the dough free and mix with a whisk.
Place the second puff pastry on top, press the edges together and coat them as well. Turn the edges of the dough inwards. Sprinkle surface with parmesan and pepper. Cover with slices of olives and feta cheese. Bake in the preheated oven (electric cooker: 200 °C/ gas: level 3) for about 30 minutes.
Serve sprinkled with basil.