Take cleaned Crab pieces and sprinkle and mix some salt and turmeric powder.
Cut Potatoes into wedges and make paste or tomatoes and Onion separately.
Take Oil in a deep bottom pan and heat the oil over medium flame.
Shallow fry potato wedges in medium flame till they turn golden in color and strain from oil and keep aside.
Shallow-fry Crab pieces in the remaining oil and keeps those aside too.
Temper the oil with the whole spices (Whole dried Red Chili, Bay leaf, Whole Cinnamon, Cumin Seed, and Whole Green Cardamom).
When the spices start spurting add onion paste to it and start cooking on a medium flame for 2-3 minutes until the onion changes color to light brown.
Add tomato paste and cook for 2 minutes and then add ginger and garlic paste to it and cook till the spices are mixed properly and the oil separates from the edges.
Add previously prepared spice paste to the pan and mix with a spatula and add 1 Tbsp. of water to it and then cook for 2-3 minutes or till the thick gravy emits an aroma and releases oil from the edges.
Now add 3 Cups of water and after mixing bring it to a boil.
Add fried potato wedges and fried Crabs and cook after covering the pan with a lid.
Cook until the potatoes are cooked properly and the gravy thickens a bit.
Adjust the water level according to taste; I prefer a bit of runny curry.
Add Ghee and Garam Masala Powder and give the curry a final mix and switch the flame off.
Serve Kakrar Jhal or Bengali Crab Curry with hot steamed rice.