Heat a few tablespoons of olive oil in a large heavy based saucepan. Sauté the lamb in batches until seared and brown on all sides, then season and remove from pan. Add a little more oil and sauté the onions and garlic slowly with a pinch of salt until softened. Stir in the Lamb Spice, sweet potato, carrot and cook for another 5 minutes. Add the tomato paste, stir everything together then return the lamb to the pan.
Add the stock and the Worcestershire sauce and bring to the boil, then reduce heat to low. Simmer covered, stirring occasionally, for 2 ½ hours or until lamb is tender. Combine the cornflour with 2 tablespoons of warm water and make a paste. Add to the lamb mixture, along with the thyme leaves, and let simmer for about 2 minutes. Remove from the heat and cool.
Preheat oven to 200°C. Grease 6 pie tins or muffin moulds with a little oil. Cut large rounds out of the puff pastry sheets to line the base of each pie tin and fill with the lamb mixture. Brush edges with a little beaten egg and top with pastry rounds to seal, then brush tops as well. Poke a small hole in the centre of the lid to let steam out of the pie, then transfer to the oven.
Bake for 20 – 30 minutes or until the pastry is puffed and golden. Let cool for about 5 min before removing from pie tins and serving with mushy peas.
For the mushy peas
While the pies are baking, put the butter in a pan and melt over low heat. Add the peas, mint and a pinch of salt.
Stir to combine, put the lid on and cook for about 5 minutes, until the peas are completely tender (fresh peas will need about 10 minutes).
Add a squeeze of lemon and mush the peas either by pulsing in a food processor or by hand, until they are thick and stodgy. Season to taste and keep warm.