Preheat your oven to 400°F (200°C).
Peel and chop the baking potato and carrot into small chunks, then boil in a pot of salted water until soft.
While the vegetables boil, finely dice the onion, slice the leeks, and chop the mushrooms.
In a large non-stick skillet, sauté the onion, leeks, and mushrooms over medium heat until they become translucent and aromatic.
Stir in the minced garlic, grated ginger, turmeric, chilli powder, and garam masala, cooking for 1 minute to release the oils.
Add the Quorn mince, frozen peas, lemon juice, gravy granules, and water to the skillet; simmer for 5-7 minutes until the sauce has thickened.
Drain the boiled potatoes and carrots, then mash them together until smooth, seasoning with a pinch of salt and pepper.
Transfer the Quorn mixture into a small baking dish and spread the root vegetable mash evenly over the top.
Bake in the oven for 15-20 minutes until the mash is slightly golden and the filling is bubbling.