Preheat the oven to 200°C/180°C Fan/gas mark 6/400°F.
Beat the egg with the flour, salt and milk to make a smooth batter.
Grease a round ovenproof pie dish, then stir half the grated cheese into the batter, before pouring it into the dish.
Bake for 30 minutes.
Take the dish out of the oven, sprinkle with the remaining cheese, and add the chorizo or pepperoni (if using) — or anything else — now, too.
Return to the oven and cook for another 2 or 3 minutes.
Once the cheese on top is melted and looks burnished gold on the crustless pizza, take it out of the oven and serve cut into slices.
