Creating Spicy Indian Butter Chicken involves marinating the chicken, preparing the sauce, and combining these to create a deliciously spicy dish. Follow these steps to achieve perfection:

Step 1: Marinate the Chicken

1. Prepare the Marinade: In a large bowl, combine yogurt, lemon juice, ginger-garlic paste, turmeric powder, red chili powder, garam masala, and salt.
2. Marinate: Add the chicken pieces to the marinade, ensuring each piece is well-coated. Cover the bowl with plastic wrap and refrigerate for at least 2 hours, preferably overnight for best results.

Step 2: Prepare the Sauce

3. Sauté Onions: In a large pan, heat butter and oil over medium heat. Add chopped onions and sauté until golden brown.
4. Add Aromatics: Stir in ginger-garlic paste and cook for an additional 2 minutes until fragrant.
5. Cook Tomatoes: Pour in the tomato puree and tomato paste, stirring well. Cook for about 10 minutes until the mixture reduces and the oil starts to separate from the tomatoes.
6. Spice It Up: Add cumin powder, coriander powder, red chili powder, and salt. Stir continuously for another 5 minutes to ensure the spices are well-blended.
7. Simmer: Reduce the heat and let the sauce simmer for about 15 minutes, stirring occasionally.

Step 3: Cook the Chicken

8. Grill or Cook Chicken: Preheat a grill or use a pan to cook the marinated chicken until it’s well done. This should take about 6-8 minutes on each side.
9. Combine Chicken and Sauce: Add the grilled chicken to the simmering sauce. Add fresh green chilies and red chili flakes for that extra kick.
10. Final Touches: Stir in the heavy cream and kasuri methi. Cook for another 5 minutes until the chicken absorbs the flavors and the sauce thickens.
11. Garnish: Finish with a sprinkle of fresh coriander leaves.