Put the flour in a large bowl and make a well in the centre. In a jug, mix the yeast, olive oil and 300ml warm water. Gradually pour into the well and mix the flour into the liquid, until it forms a soft dough. Tip out onto a floured work surface and knead to a smooth, springy dough – this will take a good 5-10 mins. Put the dough in a floured bowl, cover with a damp tea towel and leave in a warm place for about an hour until it has doubled in size.
Meanwhile, simmer the passata, garlic, basil, olive oil and a little black pepper in a pan for 20 mins until thickened. Set aside to cool.
Preheat the oven to 220°C, fan 200°C, gas 8. Knead the dough for about 2-3 mins to knock out the air. Cut into 16 pieces and roll each out to 6cm in diameter on a floured surface.
Put the pizza bases on greased baking sheets and spoon over a little of the tomato sauce.
On half of the bases, sprinkle the chopped ham, the peppers, mozzarella and basil leaves. Top the other half with the mushrooms, spinach and ricotta. Bake for 4-5 mins until the bases are golden. For other variations, try basil pesto, mozzarella and pine nuts.