Add cilantro leaves, garlic, toasted cumin seeds, kosher salt, peeled ginger, and green chilis to a blender.

Add a splash of cold water and blend on medium speed, working up to high, until smooth. Add more water if needed.

Transfer the blended chutney to a serving bowl.

Cut boneless, skinless chicken thighs into 1-inch cubes.

In a bowl, combine the chicken cubes with kosher salt, lemon juice, grated ginger, and a grated garlic clove. Mix thoroughly.

Cover and refrigerate the chicken for at least 30 minutes, or up to 2 hours.

Place whole milk yogurt in a clean tea towel, gather the sides, and tie it with kitchen twine to form a sack.

Hang the yogurt sack over a bowl to drain the whey for 2-3 hours, or overnight, until thickened.

In a large bowl, combine the hung yogurt, Kashmiri chili, turmeric powder, lemon juice, ground cumin, fenugreek leaves, coriander powder, garam masala, fine sea salt, grated ginger, grated garlic, and mustard oil.

Whisk all the marinade ingredients together until thoroughly combined into a thick paste.

Add the chicken from the first marinade to the second marinade and massage to coat evenly.

Cover the bowl with plastic wrap and refrigerate for at least 2-3 hours, or ideally overnight.

Thread the marinated chicken pieces onto metal skewers.

Grill or broil the chicken skewers for 2-3 minutes per side, turning to get an even char on all sides.

In a large pot over medium heat, melt the ghee. Add the diced onion, chopped ginger, and chopped garlic, along with a touch of salt. Sauté for 3-4 minutes until softened.

Add granulated sugar, coriander powder, cumin powder, turmeric powder, Kashmiri chili, and garam masala. Sauté for 30-60 seconds until toasted and fragrant.

Stir in tomato paste and cook for 1-2 minutes. Then add crushed tomatoes, water, and fenugreek leaves. Bring to a boil, then reduce to a simmer for 10-15 minutes.

Transfer the sauce to a blender and blend on high speed until completely smooth. Return to the pan.

Place a small bowl of melted ghee in the center of the sauce. Add a hot piece of charcoal to the ghee, cover immediately, and let it smoke for 1-2 minutes.

Remove the charcoal and bowl. Strain the smoked ghee into the sauce. Add heavy whipping cream and stir to combine.

Add the grilled chicken to the sauce and simmer for 5 more minutes. Off the heat, mount the sauce by stirring in cold, unsalted butter until emulsified.

Ladle the butter chicken into a bowl. Drizzle with a little heavy cream, sprinkle with more fenugreek leaves, and top with fresh cilantro.

Serve alongside Basmati rice, fresh garlic naan, and the green chutney.