Heat vegetable oil and one tablespoon of butter in a large pan over medium heat. Add diced chicken and cook until lightly browned on the outside, stirring occasionally. Move chicken slightly aside and melt the remaining butter in the same pan.
Add garlic and grated ginger to the melted butter and cook briefly until fragrant. Sprinkle in cumin, garam masala, paprika, turmeric, chili powder, and salt. Stir well so the chicken is evenly coated with spices.
Pour in the tomato sauce and mix everything together until smooth. Cover and let the mixture simmer gently for about 5–10 minutes so the chicken cooks through and absorbs flavors.
Remove the lid and stir in heavy cream to create a silky, rich sauce. Let it simmer uncovered for a few minutes until slightly thickened. Taste and adjust seasoning before serving.