Place mutton in a large bowl. Add yogurt, minced ginger, minced garlic, ground turmeric and red chili powder. Toss to coat. Season with salt. Cover and marinate in the refrigerator for at least 4 hours or overnight if possible.

To make tomato onion mixture, heat 1 tablespoon oil in a large frying pan or skillet over medium-high heat.

Add onions. Sauté, stirring occasionally, for about 2-3 minutes or until the onions turn light brown.

Add tomatoes and green chilies (if using). Sauté, stirring occasionally, for about 3-4 minutes or until mushy. Remove from heat. Leave to cool slightly. Place the mixture in a food processor. Process to a smooth paste. Set aside.

Meanwhile heat 2 tablespoons oil in the same pan over medium-high heat.

Add bay leaves, cinnamon stick, cloves and cardamom pods. Sauté, stirring, for about 1 minute.

Add onions. Sauté, stirring occasionally, for about 2-3 minutes or until the onions turn light brown.

Add ginger and garlic. Sauté, stirring, for 1 minute.

Add ground turmeric, ground cumin, ground coriander and red chili powder. Sauté, stirring, for a few minutes.

Add tomato onion paste. Stir to combine. Sauté, stirring occasionally, for about a minute.

When oil starts to separate, add marinated mutton. Stir to combine. Increase heat to high. Fry, stirring, for 7-10 minutes or until mutton starts to release water.

Add 1 and ½ cups water. Season with salt. Stir to combine.

Reduce heat to medium-high. Cook, covered, for about 1 and ½ hours or until mutton is tender. Add more water if necessary.

Add garam masala, dried fenugreek leaves and coriander (cilantro) leaves. Stir to combine. Heat through.

Garnish with more coriander (cilantro) leaves if you like.

Serve with steamed rice, naan, or parathas.

Make this in instant pot:Marinate mutton. Make tomato onion mixture in the instant pot on sauté mode. After step 12, cover the instant pot with lid. Cook for about 20 minutes for boneless mutton and 35 minutes for mutton with bone. Release pressure naturally. Remove lid. Stir in garam masala, dried fenugreek leaves and coriander leaves.

Make this in slow cooker:Marinate mutton. Make tomato onion mixture over stovetop. Continue cooking until step 12. After that, transfer the curry to slow cooker. Cover with lid. Cook on low for 8 hours or on high for 4 hours. Stir in garam masala, dried fenugreek leaves and coriander (cilantro) leaves.