The finished recipe. Beef and Lentil Cottage Pie with Celeriac Mash for FourIngredients 1 to 6. 350 g Beef mince, 5% fat (Weighed raw. Standard 20% mince is nearly twice the calories at the same weight.). 250 g Cooked lentils (A tin of green lentils, drained. Cooked weight, green or brown. A pouch is already this.). 500 g Celeriac (Peeled weight.). 200 g Potato (Peeled weight. A little potato stops the celeriac mash going watery. Raw, peeled weight.). 200 g Onion. 200 g CarrotIngredients 7 to 12. 400 g Beef stock (Made up from a cube or a pot.). 2 tbsp (30 g) Tomato purée. 1 tbsp, about 11 g Olive oil. A few sprigs Fresh thyme. 1 leaf Bay leaf. To taste SaltStep 1. Boil the celeriac and potato in chunks for twenty minutes until both are soft. Drain very well, steam dry for two minutes, then mash with salt, pepper and a splash of the stock.Step 2. Soften the chopped onion and carrot in the oil for ten minutes. Add the mince and fry hard until browned.Step 3. Stir in the tomato purée, thyme, bay and stock. Simmer for twenty minutes, then stir in the lentils and season.Step 4. Spread the filling in a dish, top with the mash and bake at 200°C for twenty-five minutes until the top colours.