Prepare the Chicken: Cut the chicken pieces into desired sizes, separating legs from thighs and halving each breast lengthwise.

Make Spice Paste: In a bowl, combine turmeric, ground fennel, ground coriander, and chili powder with 3 tablespoons of water to form a paste.

Sauté Aromatics: Heat oil in a pan over medium heat. Fry chopped onions, grated ginger, and crushed garlic until onions turn brown (approximately 5 minutes).

Cook Spice Paste: Reduce heat to low. Fry the spice paste, stirring continuously for 5 minutes. Add 3 tablespoons of water to the spice bowl to collect remaining spices and add this water to the pan. Stir and cook for another 3 minutes.

Brown Chicken: Increase heat to medium. Add the chicken pieces and stir-fry for 4 minutes, until the chicken changes color.

Simmer Chicken: Add salt and water, bring to a boil, cover the pan with a lid, reduce heat, and simmer for 20 minutes.

Prepare Spinach: In a separate pan, melt butter. Add chopped garlic, curry leaves, cumin seeds, fennel seeds, and chopped red chilies. Stir and add fresh or frozen chopped spinach and salt. Fry for 5 minutes.

Combine Spinach and Chicken: Add the spinach mixture to the chicken. Mix well, cover the pan, and cook for another 20 minutes.

Finish and Serve: Stir in plain yogurt and garam masala, blending well with the chicken and spinach. Cook uncovered for 6 minutes, stirring frequently, until the yogurt is fully incorporated and the sauce has thickened.