Fry 3 chopped onions till they are golden brown. Boil 2 cups soaked soaked rice in fresh water along with salt and 1 tbsp white vinegar. Boil it for 5 minutes and simmer.
Add in 1 cup oil and add in ½ kg chicken, salt, turmeric and 1 tbsp ginger garlic paste. Cook it till the water dries. Add in ½ cup yogurt, chopped tomatoes, 1 tsp red chili flakes, 1 tbsp mustard, 1 tsp nigella seeds, 1 tsp white cumin and some green chilies. add in some curry leaves and 2 lemon juice. Simmer it. At the time of serving, mix achari chicken with boiled rice and add 2 lemon juice. Dish out the rice, garnish it with fried onion and chopped mint leaves and serve.