In a broad pan put 3 tbsp oil, keep on flame. Add garlic, curry leaves, mustard, cummin and mustard seeds.
Let it splutter, add onions and braise little add tomatoes and spices. Let it cook to a paste, add potatoes and add water. When potatoes are half done add brinjal. Cook till potatoes are done.
Should be dried gravy, when done garnish with chopped green chillies and coriander leaves