In a bowl mix together flour, bicarb, salt and buttermilk. Mix together roughly with a spoon then add half the tomato sauce, half the pepperoni, the parmesan and the chopped mozzarella. Place the dough on a floured worktop and knead briefly.
Place the dough in an oiled loaf tin, then spoon the remaining sauce over the top and to with mozzarella, pepperonis and sprinkle with basil. Bake for 10 minutes then turn the oven down to 180°C/360°F for a remaining 20.