Heat a pressure cooker pan with ghee. Add cashew nuts and roast till golden brown. Drain and keep aside.
Add remaining 3 tbsp oil to the ghee.
Add bay leaf, kal paasi and the crushed spices and sauté for a minute till the aroma arises.
Add onions and sauté till pink. Add ginger garlic paste, tomatoes and 3/4 cup mint leaves and cook till the tomatoes become mushy and the mint shrinks.
Add red chili powder, coriander powder, turmeric powder and mix well.
Add the roasted baby potato mixture, salt and mix gently.
Add drained basmati rice, 3 1/2 cups water, remaining mint leaves and give it a stir.
Let the mixture start bubbling, now close the pan with a lid.
Pressure cook over medium flame for 2 whistles and switch off.
Open the lid after the pressure is released, fluff gently with a fork.
Top with roasted cashew nuts set aside.
Serve this baby potato biryani hot with any raita of your choice.