For the dough
For the topping
Put the yeast and sugar in a measuring jug and mix with 4 tablespoons of the hot water. Leave in a warm place for 15 minutes or until frothy.
Mix the flour with the salt in a large bowl, and make a well in the centre. Add the oil, the yeast mixture and the remaining water. Using a wooden spoon, mix to form a dough. Turn the dough out onto a floured work surface, and knead for 4–5 minutes until smooth. Return the dough to the bowl, cover with an oiled sheet of cling film and leave to rise in a warm place for 30 minutes or until doubled in size.
Preheat the oven to 200°C/400°F/Gas mark 6.
Remove the dough from the bowl and knead for 2 minutes. Using a rolling pin, roll out the dough to form an oval or circle shape, and put on an oiled baking tray, pushing out the edges until even. The dough should be no more than 8mm/1⁄4in thick, as it will rise during cooking.
To make the topping, put the tomatoes, garlic, dried basil and olive oil in a large heavy pan. Season with salt and pepper, and simmer for 20 minutes or until the sauce has thickened. Stir in the tomato purée and leave to cool slightly.
Spread the sauce over the pizza base, leaving a border around the edge. Top with the mushrooms, and scatter the mozzarella evenly over the top. Bake in the oven for 25 minutes, and serve hot.