In a kadahi, add 2 tbsp of oil. Add onions and fry till brown. Remove half of the fried onions for garnishing later. To the remaining, add grated ginger and garlic. Fry them.
Puree tomatoes and green chillies in a mixer. Mix into the above and cook. Add red chilli powder, coriander powder, garam masala and salt to taste.
Finally add the minced chicken( Keema) and chopped coriander. Cook till done. Leave to cool.
Preparation of Karelas
Wash and scrape the karelas. Slit and remove the seeds. Rub the karelas with about 1 tsp of salt and leave it to rest for about 20 mins. You can do this before you start cooking the keema too. Letting it sweat is important to lessen its bitterness.
Wash it nicely to remove salt and fill it with the keema/minced chicken mix. Tie the karelas with any thread so as not to spill its contents while frying.
In a pan add oil and add the karela. Shallow fry them till they turn soft and are properly cooked. Take them out on a platter
Preparation of the Keema Sauce
After the karelas have been filled with the keema, put the leftover keema in a grinder and puree it using some water.
In a pan, add about a tablespoon of oil, pour this keema sauce add 1/2 tsp red chilli powder and taste if more salt is needed. Add the 4 tbsp of milk to add gloss to the sauce.
Assembling the dish
Lay the cooked bitter gourd on a platter. Garnish with chopped fried onions kept aside. Pour the keema sauce and serve hot.