Preheat the oven to 200 ° C / 392 ° F Prepare a pie dish or bowls with Non-Stick Cooking Spray.
Stir-fry the mixed vegetables with the onion in a little olive oil.
Mix the cornflour and soup powder with a little water, when smooth, add the rest of the water, seasonings, simmer for about 20 minutes or until the vegetables are hot and cooked through, but still slightly crisp. The sauce must be of thick consistency. Adjust the seasoning to taste.
Finally add lemon juice, ground black pepper, and salt to taste. Mix the vegetables and stock with the cooked lamb.
Spoon the filling into a large, ovenproof dish or bowls and allow to cool completely.
Roll out the dough thinner and place it over the pie(s).
Squeeze the sides, make a hole or two in the crust and paint with an egg yolk-and-water mixture.
Bake for 30 minutes or until the pastry has completely puffed and is cooked.