Defrost puff pastry according to package instructions. Clean and wash the leek and blanch briefly in boiling salted water. Drain. Clean, wash and slice the zucchini and tomatoes.
Dice the cheese. Place the puff pastry slices on top of each other and roll out on a floured work surface in the size of an oval ovenproof dish. Place the puff pastry in the mould. Sprinkle breadcrumbs on top. Layer vegetables.
Put cheese on top. Mix crème fraîche and eggs and season with salt and pepper. Pour over the vegetables. Bake in the preheated oven (electric cooker: 200 °C/ gas: level 3) for about 40 minutes. Serve warm, with lamb's lettuce.