I bought a Cornish pasty a few weeks ago, and as I was munching my way through the inch-thick, tasteless, and hugely fattening semi-circular crust, I though it would be immeasurably improved by stuffing it with cheese, as is sometimes done with pizzas. Of course, you can't even think about doing that to a regular Cornish pasty without the entire population of Cornwall descending on your head, so this is not, in any way, to be mistaken for or described as a Cornish pasty. It's filled with minced beef in gravy. With cheese. The crust is stuffed. With cheese. It's delicious. With cheese.
Heat the oven to 170°C (338°F) for a fan oven, 190°C (374°F) conventional, gas 5. Take a circular dinner plate - this will be your template for the pasties. On a floured worktop, roll half of the pastry out into a thin disc. Place it on the plate and spread it so it reaches the edge or overhangs slightly. Cut off any excess. Make 2 cuts across the equator of the disc, about 3cm (just over an inch) long, one cut starting from the left edge, the other from the right. Now cut the edge of the bottom half of the pastry so that it is inset15mm (just over half an inch) from the edge of the plate. Place mozzarella near the edge of the top segment. Moisten the outside edge of the pastry with water, lift it over the cheese and press it down on the other side. The mozz should now be enclosed in a half-moon of pastry - don't forget to seal the ends.
Place a pile of filling on the top half of the pastry, inside the cheese arc. Top it with as much grated cheddar and/or mozzarella as you like. Moisten the open end of the pastry, lift it up to cover the filling, and press it down all round to seal it. Paint the top, sides and edges with eggwash (egg beaten with a splash of milk), make some holes in the top with a fork , place on a flat baking sheet and bake for 30-35 minutes until golden. You can turn the tray around halfway through to get even browning.
Flour for sprinkling. Veg oil for sautéeing.