Lentils

• Soak the lentils overnight or for 4-6 hours before cooking. Then, before cooking, rinse and drain.
• Preheat oven to 180ºC. (fan-assisted)
• Wash and pat-dry the sweet potato. With a sharp knife, stab the sweet potato all over, and bake in the oven for 40 to 50 minutes.
• Finely dice red onion, ginger and garlic.
• Wash and pat dry carrots. Cut in half lengthwise, then cut each half down the centre lengthwise and finely slice.
• Roughly chop the cooked chestnuts.
• Chop the green chillies, including the seeds.
• In a shallow cast-iron casserole dish, heat the oil. Add Tej pasta (Indian bay leaf), cloves, and cassia bark, then, 1 minute later, add cumin seeds, followed by chopped onions. Fry the onions until soft and golden brown.
• Now add the chopped garlic and ginger and fry for a minute or two.
• Add the sliced carrots and cook for a minute or two. Follow with the chopped tomato, chopped green chillies and the soaked and drained lentils.

  Season with 1 teaspoon salt and add vegetable stock.

  Cover and cook over a medium heat for 10 minutes, or until the lentils are soft to the touch but not al dente.
• Add the chopped chestnuts, garam masala and chilli powder. Give it a good mix. Check the seasoning -add more salt if required - and add the juice of half a lemon.
• Cook uncovered for another 10 minutes over medium-low heat, stirring occasionally to prevent anything from sticking to the bottom of the pot.
• Remove the sweet potato from the oven. Push a knife through to check if it's fully cooked. Cut the potato in half lengthwise and remove the skin. Transfer the potato flesh into a bowl along with butter, one teaspoon of salt, and crushed black pepper. Using a fork or potato masher, mash the sweet potatoes, into a smooth puree.
• Remove the lentils from the stove, then remove the cassia bark, the black cardamom pod, and the tej patta.

  Using the back of a spoon, smooth the surface of the filling.

  Spoon in the sweet potato mash. Spread the mash evenly, then use the fork to create ridges; these will go crispy in the oven.
• Transfer the casserole dish to the oven and bake for 30 minutes, or until the sweet potato has a golden-brown colour.
• Garnish with chopped coriander (optional) and serve hot.