First, clean the pieces of mutton well and transfer them into a large mixing bowl.

To this, add the sour curd or yogurt, ginger garlic paste, mustard oil, turmeric powder, garam masala, and salt to taste.

Combine and mix everything thoroughly.

Coat all the pieces of mutton with the marinade. Make sure not to miss any corner.

Cover the bowl and keep aside. Let the mutton rest for about an hour or more.

While the mutton is resting, peel and cut the onions into thin slices.

Take a blender and make a paste of the ginger, garlic, and 4-5 green chilis. Keep them aside.

Next, take a large Kadhai and add oil.

Keep the flame on medium and let the oil heat until it smokes a little.

Now, to the oil, add the bay leaves, dried red chilis, cloves, green cardamom, black cardamom, and the cinnamon stick (break into 2 pieces).

Stir all these until fragrance comes out of the aromatics.

Next, add the sliced onions.

Stir and fry them until golden brown in color. Keep the flame on medium. This should take around 12-15 minutes.

To this add the ginger, garlic, and green chili paste.

Combine everything nicely and fry them for about 5 minutes or until the raw smell is gone.

By now, the onions will start to caramelize.

Take a small bowl and add the cumin powder, coriander powder, and Kashmiri red chili powder.

Add 2 tbsp of water and make them into a slurry.

Add the slurry to the kadhai. Mix nicely.

Fry everything until the oil starts separating from the masala.

Now, add the marinated mutton to the kadhai. Keep the flame on medium.

Stir continuously and scrape from all sides to combine the masala and the mutton pieces.

Cook the mutton for about 10-15 minutes with consistent stirring.

Take a bowl and put the sour curd or yogurt into it. Whisk it until smooth and creamy.

Pour the whisked curd into the kadhai and combine nicely.

Next, add salt to taste and sugar to taste to balance the salt.

Mix and stir from all the sides.

Heat up 1 cup of water (can be more).

When the moisture of the masala starts to get dry add a splash and stir.

Now, let the mutton cook on a medium flame for about 60 minutes.

Keep the kadhai covered and let them cook.

Occasionally stir and when the masala dries out add some amount of hot water to the kadhai.

After 60 minutes, check if the mutton is cooked. If not, cook it for 30 more minutes.

Take a taste test and add if anything is needed.

When the dark color appears, add half a cup of hot (you can add more) water for the gravy. Do not add too much as we want a thick consistency for the mutton kosha.

Slit two green chilis and add in the kadhai.

Cover again and cook until the mutton is cooked to perfection.

When it is done, transfer it into a bowl.

Garnish the mutton kosha with ghee and cover the bowl. Let the flavors incorporate well.