Make your spice mix. Measure out all the spices, kasoor methi and salt and toss them into a little bowl. It's all going in at once.
Pre-heat a skillet large enough to hold all the ingredients over medium-low heat. Pick a skillet that has a lid. Add the oil.
When the oil starts to shimmer add the garlic ginger paste. Cook, stirring continuously, until it stops sputtering. This part can get a bit messy. Stand back. You want to drive the water out and cook the paste a bit. You don't want it to colour up.
Add the spice mix. All of it. Stir to combine and fry for about 30-45 seconds. You want the spices to fry in the oil If it looks dry or it's starting to stick reduce the heat and add more oil. You are blooming spices. This is where the magic happens. If you don't have a really good hood fan your house should smell like an Indian restaurant at this point.
Add the hotel gravy and the makhani gravy. Stir to combine. Get the oil worked into the sauce. Cover and simmer for 5 minutes.
Stir in the coconut milk and brown sugar and then add the chicken tikka. Cover and simmer until the chicken tikka is warmed through.
Add the heavy cream if using.
Look at the consistency of the sauce. If you would like it a bit thinner add a bit of chicken stock and stir. You probably won't need any if you are using the heavy cream. Simmer for about a minute.
Serve with rice and naan or chapatis. A nice chana masala or tarka dal is always good too.