Mix the flour, yeast, sugar, salt and approximately 250 ml lukewarm water and knead to a dough. Cover and put in a warm, draught-free place to rise for about 1 hour. Then knock back (knead again) and leave to rise for a further 30-40 minutes.
Line a baking tray with baking parchment. Dust a work surface generously with flour and divide the dough into 16 balls. Roll the balls out to circles with a rolling pin and place on the baking tray.
Flatten evenly with your hands, making the edges a little thicker than the middles. Spread the pizza bases with a little creme fraiche and season with salt and pepper.
For the topping:
Arrange the tomato slices on the pizza bases and scatter with mozzarella slices and chopped olives. Add a few small blobs of pesto and sprinkle with a little olive oil. Bake in a preheated oven (220°C) for 8-12 minutes, or until golden brown. Serve garnished with basil.