Sauce: Heat the vegetable oil and fry the onion and garlic until soft. Stir in the tomato purée and cook for a further 5 minutes. Add the soy sauce, Madeira and stock and bring to the boil, then add the lentils. Reduce the heat, cover and cook for 25 minutes, or until lentils are soft.Stir the thyme into the sauce and season to taste Veg: Peel and chop the veg and cook til JUST tender in veg stock Topping: Par-boil the potatoes in lightly salted boiling water. And toss in oil. Assembly: Layer sauce, then vegetables, finishing with spuds. Place the dishes under a preheated hot grill or in even until the potato topping looks golden.