Step 1: Marinate the Chicken — In a large bowl, whisk together the yogurt, ginger garlic paste, Kashmiri red chili powder, and salt until completely smooth — no lumps, or the yogurt can split later. Add the chicken pieces and turn until every piece is well coated. Cover and refrigerate for at least 30 minutes, or up to 4 hours for deeper flavor.
Step 2: Bloom the Whole Spices — Heat the ghee in a heavy, deep pan or Dutch oven over medium heat. Add the green cardamom pods, black cardamom, cloves, cinnamon stick, and bay leaves. Sizzle for 30–45 seconds until fragrant — this quick tadka perfumes the ghee and is the foundation of the curry's aroma.
Step 3: Brown the Chicken — Shake excess marinade off the chicken (reserve the marinade — it goes back in). Add the chicken pieces to the pan in a single layer and sear for 4–5 minutes, turning once, until lightly golden at the edges. If using the optional onion, add it now and cook 5–6 minutes until soft and golden. Stir in the remaining ginger garlic paste and cook 1 minute more.
Step 4: Add the Rogan Josh Masala — Lower the heat and sprinkle in the ground fennel, dry ginger powder, garam masala, ground cardamom, and black pepper. Stir for 30 seconds until the spices coat the chicken and smell intensely aromatic. Pour in the reserved yogurt marinade, stirring constantly as you add it so the yogurt blends in smoothly instead of curdling.
Step 5: Slow Cook Until Tender — Pour in 1 cup of water and bring to a gentle simmer — never a hard boil, which can split the yogurt. Cover, reduce the heat to low, and cook for 25–30 minutes, stirring once or twice, until the chicken is completely tender and the ghee begins to glisten at the edges of the gravy. If the gravy gets too thick, splash in a little hot water; if too thin, simmer uncovered for 5 minutes.
Step 6: Finish and Serve — Taste and adjust salt. Fish out the bay leaves and cinnamon stick if you like. Transfer to a serving bowl, drizzle with a teaspoon of warm ghee, and garnish with fresh cilantro. Serve hot with steamed basmati rice or naan.