1Heat butter and oil in a pan, add mustard seeds, and sauté until they start to pop.
2Add chopped onions and sauté until edges start to brown slightly.
3Stir in ginger and garlic paste.
4Add spices (coriander, garam masala, ground cumin, salt, red chilli mix, and optional kasuri methi) and stir, ensuring heat is low to prevent burning.
5Add blended tomatoes and cook until excess water evaporates.
6Reduce heat and stir in yoghurt.
7Add chopped aubergines and potatoes to the pan and mix until well coated.
8Add about 60 to 80 milliliters of water and green chillies, then give a quick stir.
9Cover with a lid and cook for 10 minutes.
10Sprinkle with fresh coriander and stir gently to combine.