Fry the onion and celery on a medium heat in a little oil until transparent. Add the meat, increase the heat, and fry until browned, breaking it up with a wooden spoon. Add remaining ingredients (except pastry and egg), turn down the heat and simmer gently until cooked (about 45 minutes, but the longer the better). Remove the bay leaf and lemon zest.
Preheat the oven to 200ºC, grease baking tins. Use pastry to line greased pie tins, fill with meat mixture, then cover each with a round of pastry and press around the edge to seal. Brush with beaten egg.
Bake in the oven until the pastry is crisp and golden.