Roll out your pastry and, cutting round a saucer, make six rounds.
Mix the mince, onion and potato. Season your mixture to taste, then divide it between the six rounds, placing it to one side of the pastry so that you can easily fold it over.
Place two or three slices of tomato on top of each pasty’s filling. Damp the edges of the pastry, then fold it over and pinch the edges together to make a seal.
Brush each pasty with beaten egg, make a couple of slits in the top of each pasty then bake until golden brown (around 30 minutes).