Marinade your chicken overnight with the first half of the spices, the yoghurt, oil, 2 tbsp garlic/ginger paste and the sliced onion.
The next day, skewer your meat and cook over coal slowly
To make the sauce, sweat the diced onion right down, then add the remaining ginger and garlic paste, tomatoe paste, and remaining spices. Once fragrant add the tomatoes, and leave to simmer for around 5 minutes.
You can now add the heavy cream, stir through, and by now the chicken shoudl be around 80% done. Remove from the skewers and stir into the sacue
After 10 more minutes, the curry should be ready to serve alongside garlic naan.