In a large saucepan, sauté onions + garlic with a pinch of salt + pepper in the olive oil until lightly browned.
Add lentils, carrots, stock, gravy + parsley + stir. Simmer until lentils are tender (about 30 mins). Stir in the peas + thicken with cornflour mixed with water if needed.
Meanwhile, peel the potatoes + slice any large ones in half. Place in a large pot + cover with water. Bring to a simmer, then salt, cover + cook for 20-30 minutes or until very tender.
Heat the oven to 180°C / 160 °C Fan.
Once the potatoes are cooked, drain and mash with vegetable margarine, soya milk, salt + pepper.
Transfer the lentil mixture to a baking dish and carefully top with mashed potatoes. Smooth down with a fork.
Place the dish on a baking tray and bake for 15 minutes or until the mash is lightly browned on top.