Make Potato Pattice: Mash the potatoes well and add ginger+garlic paste, ground coriander, ground cumin, chaat masala and salt. Mix well, add enough bread crumbs and knead into a smooth, pliable dough. Divide the mixture into big lemon size balls and flatten them in the palm of your hand. Set them aside on a plate.
Heat a tawa or griddle on medium flame. Add 2~3tsp oil and place the prepared patties on the hot tawa and cook until golden brown crust forms on both sides. Keep them warm while you prepare the Ragda.
Make Ragda: Pressure cook soaked peas until tender, but not too mushy. Heat 2tbsp oil in a pan; add onions and cook until onions are soft and turn golden brown.
Stir in ginger+garlic paste, turmeric, red chili powder, garam masala, chaat masala and cook for 1~2 minutes.
Next add chopped tomatoes, tomato paste and salt. Cook covered till tomatoes are soft and mushy.
Add the cooked peas and 1cup water. Bring the mixture to a boil and simmer for 4~5 minutes.
Finally add the whisked yogurt and mix well. Simmer for 2~3 minutes and turn off the heat.