Step 1: Build the Sauce Base — Add the chopped onion, ginger garlic paste, tomato sauce, water, and all the spices — garam masala, cumin, smoked paprika, Kashmiri chili powder, turmeric, coriander, and salt — directly to the slow cooker. Stir until the spices are evenly distributed through the tomato sauce.

Step 2: Add the Chicken — Add the chicken thigh pieces and toss until every piece is coated in the spiced tomato sauce. No searing, no browning, no pre-frying — that's the whole point.

Step 3: Slow Cook — Cover and cook on LOW for 6–8 hours or on HIGH for 3–4 hours, until the chicken is fork-tender and shreds easily at the edges. Avoid lifting the lid during the cook — every peek adds 15–20 minutes of cooking time.

Step 4: Blend the Sauce — Transfer the chicken pieces to a plate with a slotted spoon. Blend the sauce directly in the slow cooker with an immersion blender until completely smooth (or blend in batches in a regular blender, venting the lid so steam escapes). This one step transforms a slow-cooker stew into a restaurant-style creamy gravy.

Step 5: Finish Creamy — Stir in the coconut milk (or heavy cream), the yogurt if using, lemon juice, and butter or ghee. Return the chicken to the slow cooker, cover, and cook on LOW for 10–15 more minutes so the flavors meld. Taste and adjust salt.

Step 6: Serve — Spoon over steamed basmati rice or serve with warm naan. Garnish with chopped cilantro and a swirl of coconut milk or cream.