Pre-heat the oven to 200°C/ fan 180°C. Unroll the pastry, cut into six squares and arrange over two baking trays lined with baking parchment. Use a knife to score a 1cm border around the edge of each pastry square. Bake for 15 mins, until puffed up but not cooked through.  
 

While the pastry cooks, make the sauce and prepare your toppings. Mix the tomato purée, tomato ketchup, oregano and 1 tbsp water. Grate the cheese and chop any veg or herbs you want to put on top into small pieces. Set aside. 
 

Remove the pastry from the oven and squash down the middles with the back of a spoon. Divide the sauce between the pastry squares and spread it out to the puffed-up edges. Sprinkle with the cheese, then add your toppings. Bake for another 5-8 mins and serve.