Add 2 tbsp of butter in a large skillet over medium-high heat and, working in batches, cook the chicken until browned. Set aside.
Melt another 2 tbsp of butter in the pan over medium heat. Add the onion, and cook for 2-3 minutes or until beginning to soften. Add the garlic, garam masala, ginger, chili powder, cumin, cayenne and sugar. Stir to combine, and cook for about 45 seconds before adding the passata.
Bring the sauce to a simmer and let cook for 5 minutes before adding in the cream. Bring the mixture back to a simmer, return the chicken back to the pan and let simmer for 10-15 minutes. Keep the heat low here and don’t boil it too hard.
Stir in the remaining 2 tbsp of butter and season with salt and pepper, to taste. Serve with rice, naan bead or papadums.
