Set the Instant Pot to saute mode, and add in the oil to heat. Saute onions, ginger and garlic till soft and lightly browned.
Add in tomato paste, chilli powder and salt, and fry for a few seconds to mix everything well.
Add in the chopped tomatoes and cook for a few minutes till the tomatoes soften and start to pulp.
Add in pre-soaked lentils and kidney beans, and about 2 cups of water to cover them. Put on the lid and set the Instant Pot to Manual Pressure mode, and make sure that the valve is in the sealing position. Set the pressure timer to 20 minutes and let it cook.
Once the timer goes off, let the pressure release naturally, then slowly stir in milk and let it come to a boil, adding in more water if necessary depending on the consistency you prefer. Garnish with fresh coriander leaves and serve warm.