Prep the Peas: Soak the dried white peas overnight. Drain the water and rinse well.
Make the Bhaja Masala: Dry roast cumin, coriander seeds and dry red chilies until fragrant. Cool and grind the spices into a fine powder.
Boil the peas: Combine soaked peas, potato, turmeric, Kashmiri red chili powder, ½tsp Bhaja masala, grated ginger and green chilies in a heavy bottom sauce pan or the pressure cooker. Bring to a boil, lower the heat and simmer for 20~25 minutes or until the peas and potato are tender, but not mushy. Alternately pressure cook for 3~4 whistles. Set aside. Do not discard the cooking liquid.
To make Ghugni: In a pan, heat 2tbsp mustard oil, add the cumin seeds and once the seeds start to splutter, add the chopped onion and cook till they turn lightly browned around the edges. Stir in the minced garlic and cook for 1 minute.
Next add the chopped tomatoes, 1tsp Bhaja masala and salt; cook till the tomatoes get mushy and the oil starts to separate around the edges.
Next add the boiled peas and potatoes along with aamchoor or tamarind paste and ½cup of cooking liquid. Simmer for 10~15 minutes or until the peas are completely tender and soft. Add more cooking liquid if the ghugni gets too thick.
Taste and adjust the spices and seasoning as needed. By the time the ghugni is done cooking, it should have a thick consistency.
To Serve: Spoon ghugni into serving bowl and top with finely chopped onion, green chilies, squeeze of lemon and an optional egg. Enjoy!!