In a large non-stick pan over medium-high heat, add coconut or olive oil. Sauté diced yellow onion, ginger paste, and minced garlic until the onion is golden and fragrant.

Stir in smoked paprika, ground cumin, ground turmeric, salt, and garam masala. Sauté until the spices become fragrant.

Add diced tomatoes to the pan, scraping up any browned bits. Simmer briefly until it thickens, then let cool slightly before transferring to the slow cooker.

Trim excess fat from chicken thighs and place them in the slow cooker. Pour the cooled onion-tomato mixture over chicken.

Cook your Crockpot Butter Chicken on high for 2.5 to 4 hours or low for 4 to 6 hours until chicken is cooked through.

Remove the chicken, chop into bite-sized pieces, and use an immersion blender to purée the cooking liquid until smooth.

Stir in unsalted butter and heavy cream into the sauce, returning chopped chicken back to the slow cooker.

Serve the Crockpot Butter Chicken over fluffy rice or with warm naan, garnished with fresh cilantro.