Peel and chop the potatoes and add them to a pot. Cover with water and bring them to the boil. Cook for around 20-25 minutes until the potatoes are soft and cooked.
While the potatoes are cooking, start making your mince.
Add the mushrooms to a food processor and process until finely chopped.
Add the onion and garlic to a pot with the olive oil and sauté until the onions are softened.
Add the soy mince or TVP and sauté with the onion and garlic until soft and browned. If your soy mince is a bit chunky then use your spatula while sautéeing to break it up into small pieces.
Add in the chopped mushrooms, soy sauce, maple syrup, basil, oregano and tomato paste and mix in.
Add the frozen peas and carrots and sauté with the veggie mince until the peas and carrots are slightly softened.
When the potatoes are cooked, add in the vegan butter and soy milk and mash it up. Add sea salt and black pepper to taste.
Preheat the oven to 390°F (200°C).
Add the veggie mince to a pie dish (a square or rectangular dish will also do fine) and smooth down.
Add the mashed potatoes on top and smooth them down as the top layer. Use a fork to create ridges in the mashed potatoes.
Dot with some vegan butter on top and sprinkle with black pepper.
Place into the oven to bake for 30 minutes. In the last 5 minutes switch over to grill for some extra browning on top.