Heat oil in a pressure cooker, add cumin, mustard, nigella seeds and once they splutter, add ginger, green chillies and saute for a few seconds till fragrant.
1 tablespoon groundnut oil or any neutral flavoured oil, ¼ teaspoon cumin seeds, ¼ teaspoon mustard seeds, ¼ teaspoon kalonji, 1 tablespoon finely chopped ginger, 2 green chillies
Add tomatoes and spice powders - turmeric, coriander, cumin, red chilli, saute for 2 minutes. Cook covered with the lid for 5 minutes till the tomatoes turn mushy.
1 cup chopped tomatoes, ½ teaspoon turmeric powder, 1 teaspoon coriander powder, ½ teaspoon cumin powder, 1 teaspoon red chilli powder
Add potato cubes, green peas, salt, stir well, add water and close the lid of the pressure cooker. cook on high till the first whistle and on low for 3 whistles till the potatoes and peas are cooked well. Let the cooker depressurize by itself, add coriander leaves, mix and serve.
2 potatoes / aloo, ½ cup green peas / matar, ½ - ¾ teaspoon salt, 1 cup water, 2 tablespoons finely chopped coriander leaves