Put 7g sachet fast action dried yeast in a bowl or jug with 1tsp caster sugar and 225ml lukewarm water. Leave to rest for 5-10 mins (yeast will start to foam).
Put 350g strong flour in a bowl with 25g semolina and 1tsp salt. Gently mix together. Make a well in the centre and add the yeast mixture and 1tbsp olive oil.
Bring together into a ball with a wooden spoon, and knead the dough for 10-15 mins. When smooth, put in a lightly oiled bowl, cover and leave to rise for 1 hour.
Remove dough from the bowl and split into 2 balls. Knead for a few minutes, place onto an oiled baking sheet, cover with oiled clingfilm and leave to rest for 20 minutes.
Drain a tin of 400g chopped tomatoes. Peel and finely chop 3 cloves garlic and mix with the tomatoes and 2tsp tomato puree in a bowl. Season with salt and pepper. Chop chillies, mushrooms etc to taste).
On a lightly floured surface roll out each dough ball to your preferred size & thickness. Sprinkle some semolina onto baking sheets and lift the pizzas onto them.
Spread tomato mixture onto each base, tear mozzarella and place on with rest of the toppings (sprinkle mixed herbs or basil on top). Brush the crusts with some olive oil. Bake in oven for 10-15 mins on gas 7 or 220C.