Heat olive oil in a large frying pan over medium-high heat. Add onion, mushrooms and carrot and cook until softened and browned.
Add beef mince and garlic and cook until the beef is browned, breaking it up as it cooks.
Stir through the tomato paste, then add the tamari, beef stock and bay leaves. Stir to combine.
Simmer uncovered for 10–15 minutes, or until the mixture has thickened.
Add the frozen peas for the final 3–4 minutes of cooking. Remove the bay leaves.
Meanwhile, prepare the mash. Place chopped potatoes in a microwave-safe bowl with 2–3 tbsp water and a little salt. Cover loosely and microwave for 5–8 minutes, or until soft.
Drain the potatoes, then mash with the butter, milk, salt and pepper until smooth.
Divide the beef and vegetable filling evenly between 4 freezer-safe containers. Top each with mashed potato.
Allow the pies to cool completely, then seal and freeze.
To cook from frozen: Preheat oven to 190°C fan-forced. Place the pies on a baking tray and loosely cover with foil. Bake for 50 minutes.
Remove the foil and bake for a further 10 minutes, or until the potato is golden and the filling is piping hot throughout. Enjoy!