Mix the pizza base mix with water together in a large bowl, to make dough. Place on a floured surface and knead for 5 mins until smooth. Cut into 2 pieces then roll out on a floured surface to 18cm wide circles. Place on a baking sheet and leave in a warm place for 10mins until it puffs up.
Preheat the oven to Gas 7, 220, fan 200°C. Spoon 2tbsp of the sauce onto the pizzas then spread over the dough, leaving a 1cm border clear around the edge. Scatter over the grated cheese and top with ham and mushrooms. Finally use your fingers to scatter over the oregano and use a teaspoon to drizzle a little olive oil all over the toppings.
Put the pizzas in the oven and bake for 10-12mins or until golden brown and crisp. Leave to cool for 5 mins before serving.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home.