Preheat oven to 200 degrees celsius (fan-forced).
Place the peeled onion, potatoes and carrots into the Thermomix bowl and chop on Speed 8, 8 seconds.
Add the lamb mince, frozen peas and corn, Worcestershire sauce and vegetable stock and mix on Reverse, Speed 4, 10 seconds. Scrape down the sides of the bowl and repeat until combined (you'll need to use the spatula to help mix).
Use a dinner plate to cut 1 large round out of each pastry sheet.
Divide the mixture between half of each circle, brush the edge with egg and fold over to seal. Use a fork to create a crinkled sealed edge.
Brush the pastry with egg and sprinkle with sesame seeds.
Bake for 30 minutes or until golden brown and cooked through.
Serve hot with tomato sauce or chutney.