Preheat the oven to 190°C/gas 5. Prepare all the vegetables and slice the cheese for the toppings.
Add the flour and bicarbonate of soda to a mixing bowl.
Thoroughly mix in the yogurt and 75ml water. Shape into eight small balls and roll into rounds, using a little flour to stop them sticking.
Place on a lightly oiled baking sheet and spread with tomato puree then add a slice of tomato, sprinkle with oregano. Scatter with onion and sweetcorn and top each with a slice of mozzarella.