In a large pan over medium heat, warm vegetable oil or ghee. Add finely chopped onion, minced garlic, and grated fresh ginger. Sauté for about 5 minutes until the onion turns sweet and translucent.

Stir in garam masala, ground cumin, ground coriander, turmeric, smoked paprika, and salt. Cook for 2 minutes, stirring continuously.

Add chicken thighs to the pan and stir to coat with the spice mixture. Let brown for about 5 minutes.

Transfer the browned chicken and spice mixture into your slow cooker.

In the slow cooker, stir in crushed tomatoes, coconut milk, and tomato paste. Mix until well combined.

Cover the slow cooker and cook on low for 6–8 hours or on high for 3–4 hours.

Once cooking time is complete, stir in the juice of half a lemon. Adjust seasoning if necessary.

Ladle the creamy chicken tikka masala into bowls and garnish with fresh cilantro. Serve hot alongside basmati rice or naan.