This is a fab recipe for leftover roast lamb, or roast beef (just use beef stock instead of lamb stock). If I can't be bothered making mash then we serve the lamb/beef sauce over baked potatoes instead. It's a delicious, tasty and fairly low faff dish - and you can freeze the leftovers, if there are any.
1/2 cup green lentils
250ml lamb stock
400g tin chopped tomatoes
1 tsp soy sauce
1 tsp Worcester sauce
60ml red wine
1 large onion, chopped
2 stalks celery, chopped
2 large carrots, chopped
2 cloves garlic, chopped
Handful or two of frozen peas
500g or more leftover roast lamb, chopped into smallish chunks
3 or 4 large floury potatoes
Grated cheese to mix in with the mash
Heat a little olive oil in a large, heavy-based saucepan over a medium heat and sweat off the onion, garlic, celery and carrot until they start to soften but not brown.
Add the tinned tomatoes, stock, water, lentils, soy sauce and Worcester sauce. Bring to the boil, then reduce heat and simmer gently for around 30 minutes. Add the red wine and simmer for a further half an hour. You should end up with a rich, flavoursome sauce without too much liquid.
Preheat oven to 180°C. Add the leftover lamb to the sauce, along with the frozen peas and let everything warm through on a low heat whilst you cook the potatoes. Peel and chop potatoes into even-sized pieces, cover with cold water and bring to the boil in a large pot. Cook the potatoes until they are tender, then drain, mash and season to taste. Mix a good handful of cheese into the mash, beat it in with a fork so it's evenly distributed through the mash.
Spread the meat mixture in the bottom of a large casserole dish and spread the potato mash over the top. Sprinkle over some grated cheese. Put in oven and cook until the top has crisped up, browned slightly, and everything is well heated through. This usually takes about 20 minutes. Take your shepherds pie out of the oven, let it cool for 5 minutes, and then serve it with a side salad.