Add all spices for garam masala to a dry pan and roast over medium heat until warmed through and fragrant. About 10 minutes.

Allow spices to cool and process in a spice grinder in batches until a smooth powder.

Pass powder through a finely meshed sieve to remove any large bits.

Store garam masala in an airtight container until ready to use.

Heat oven to 200C.

Cut the root ends of the bulbs of garlic and place them cut-side down on a large piece of aluminum foil.

Drizzle garlic cloves with a bit of olive oil and wrap the ends of the foil around the tops of the bulbs, creating a sealed package.

Cook garlic in the oven for about an hour until all cloves are nicely browned and completely tender.

Allow garlic bulbs to cool until cool enough to handle.

While garlic is cooling, peel and roughly chop the ginger and add to a food processor or blender.

Heat butter and ghee in a pan and stir in the ground chili, cook for about a minute, making sure it doesn't burn and leave mixture to cool.

When cool, squeeze all cloves of two bulbs of roasted garlic from their shells into the food processor (they should plop out easily).

Process garlic and ginger into a smooth paste.

In a large bowl, combine yogurt, garlic/ginger paste, butter/chili mixture, garam masala, salt and ground fenugreek leaves and mix to a uniform marinade.

Cut a few slashes into each chicken thigh to allow better penetration, then dump the chicken into the marinade, tossing and massaging the meat to ensure full and even coverage.

Leave chicken to marinade overnight or up to 24 hours.

Heat ghee or butter over low heat in a large pot and add the onions along with a teaspoon of salt.

Cook onions over low heat for about 45-60 minutes until completely soft and lightly caramelized.

Add tomato paste and continue to cook for about five minutes.

Add ground chili, ginger, garam masala, fenugreek seeds and tumeric, then continue cooking for about five minutes till fragrant.

Squeeze the remaining roasted garlic into the pot (discarding the husk, obviously) and stir to combine.

Add chopped tomatoes, raise heat to bring pot to a simmer, then back heat down to achieve a light simmer.

Simmer sauce base uncovered for an hour or two until bright red, slightly reduced and intensified in flavor.

Back the heat down to a bare simmer as you prepare to grill the chicken.

Remove the chicken from the fridge and let it rest at room temperature.

Bring a grill or a home oven set to broil to as high of a temperature as you can possibly master.

Remove chicken from the marinade and brush off most but not all.

Working in batches if needed, grill chicken at vigorously high heat. If using a home oven, place chicken as close to the broiling element as possible.

Continue cooking chicken for a few minutes per side until browned on the outside but not cooked through.

Remove chicken from the heat and carefully transfer to the simmering sauce.

Add the remainder of the yogurt along with the heavy cream and coconut milk to the pot and bring things back to a simmer.

Simmer chicken pieces in the sauce-base uncovered for about an hour or until completely tender when poked with a fork or knife.

If using bone-in chicken, you may at this time carefully lift chicken from the sauce and extract the bones, returning only the meat to the sauce.

Break the butter into small cubes and whisk them into the sauce a few at a time to create a rich, creamy finish.

Taste for seasoning and add salt and pepper if needed - then serve immediately over perfectly cooked basmati rice.