Mix the yeast with the sugar and 350ml lukewarm water. Stir in 4-5 tbsp flour and leave to stand for 20 minutes. Mix the remaining flour, semolina and salt in a bowl. Add the yeast mix and knead everything to a smooth, soft dough. Shape into a ball, cover the bowl and leave to rest in a warm place for about 1 hour.
Peel the onion and cut into thin rings.
Scald the tomatoes in boiling water, drain, peel, deseed and finely dice the flesh.
Saute the onions in hot oil in a pan until softened. Add the tomatoes and cook for another 5 minutes. Remove from the heat and add the basil.
Drain the anchovies and pat dry with kitchen paper.
Drain the olives. Peel and finely chop the garlic.
Line 2 baking sheets with baking paper. Preheat the oven to 220°C (200°C fan, gas 7). Spread a thin layer of flour and semolina on the work surface. Knead the dough briefly, shape it into a ball, divide into 10 portions and roll into balls. Leave to rest on a lightly floured surface for another 20 minutes. Flatten the dough pieces with your hands.
Garnish the mini pizzas with olives and anchovies. Scatter over the garlic.
Spread the tomato and onion mixture on the pizzas with a spoon. Tear the drained mozzarella into small pieces and place on the pizzas.
Grate the pecorino over the pizzas and place them on the baking tray. Bake in the oven for 15 minutes until golden brown and crisp.