Bring one cup of water to the boil with 1 tablespoon salt. Pour over the textured vegetable protein (TVP) in a bowl, cover and let soak until soft.
Rinse the TVP with cold water then squeeze with your hands to remove most of the water content. Repeat. Cut the TVP into bite-sized pieces.
Heat 4 tablespoons oil in a saucepan then add the mustard seeds and garlic. Add the lentils and fry until they are light brown. Add the curry leaves and fry lightly. Add the onion and fry until browning.
Add the ginger and green chilli and fry 20 seconds. Then add tomatoes and fry another minute. Add 1/2 tablespoon turmeric powder, stirring constantly. If curry is sticking, splash in a little water.
Add the potato and stir, then season with salt and chilli powder to taste. Add 1/2 cup water and simmer until the water is absorbed and the potato is cooked. Add the TVP, stir well for 2-3 minutes.