Step 1

Heat oil in a large heavy-based saucepan over medium heat. Add the rosemary and cook, stirring, for 30 seconds. Reduce the heat to medium-low, then add the chopped onion. Cook, stirring occasionally, for 10-12 minutes until soft and light golden. Add the garlic and Vegemite, and stir for 1 minute to combine. The Vegemite will act as a stock base and give the filling colour.

Step 2

Season the lamb with freshly ground black pepper. Increase the heat to medium and add lamb to the pan, turning with a spoon for 3-4 minutes until the meat is sealed. (By ‘sealed’ I mean until the meat has turned a pale colour, not browned – if you brown it at this stage, you increase the chance of giving the filling a bitter flavour.)

Step 3

Add 2 litres (8 cups) water and bring to a simmer. Turn heat to medium-low, cover and cook for 1 1/2 hours or until the meat is very tender. Add the potato and simmer for 15 minutes or until tender.

Step 4

In a small bowl, mix the cornflour with 1/4 cup (60ml) water to make a wet paste, then rapidly stir the paste into the lamb filling and cook for 10-20 seconds until the mixture has thickened. Stir in the frozen peas, then remove the pan from the heat and allow to cool.

Step 5

Preheat the oven to 175°C. Choose a container to bake your pie in that will hold all the filling and is about 5cm deep (we used a 14cm x 26cm rectangular baking dish, or try a deep 24cm pie dish). Rub the inside with a little butter.

Step 6

Place the shortcrust on a lightly floured surface, overlapping the 2 pieces slightly to form a long rectangle. Using a rolling pin (if you don’t have one, use a clean wine bottle), roll over the join to seal the two sheets together, then use to line the pie dish, pressing gently into the corners.

Step 7

Spoon the filling into the pie dish. Place the puff pastry on a lightly floured surface, overlapping the two pieces slightly to form a long rectangle. As before, roll over the join to seal the two sheets together. Brush the rim of the shortcrust with a little beaten egg yolk, so the lid will stick to the base. Lay the puff pastry sheet over the pie dish, crimp the edges of the puff and shortcrust together by pressing down with a fork, then trim away any excess pastry.

Step 8

Glaze the pie by brushing with the remaining egg yolk. Slash the top of the pastry in 3 places, so that steam is able to escape and the pastry puffs. Place the dish on a baking sheet and bake for about 45 minutes or until the pastry top is golden brown. Let the pie stand for 10-15 minutes, then cut and serve.