Mini Olive, Mozzarella and Ham Pizzas

For the dough: Place the flour in a bowl with the yeast, sugar, salt and 250 ml (approximately 1 cup) of lukewarm water and knead until smooth. Cover and let stand in a warm draft-free spot until doubled in bulk, about 1 hour. Knead the dough, cover and let rise again for 30-40 minutes. Preheat the oven to 220°C (approximately 425°F). Line two baking sheet with parchment paper. Generously flour the work surface and divide the dough into 16 balls. Roll out with a rolling pin and flatten evenly with your hands, leaving the edge a little thicker. Place the dough on the baking sheets, spacing them 2 inches apart. Brush the dough with a little olive oil. Spread the tomato puree on the mini-pizzas and season with salt and pepper.