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 and view the full Food safety at home video.