Gather all ingredients. Place chicken in a bowl. Drizzle vegetable oil over chicken; toss to coat.
Whisk together salt, garam masala, cumin, coriander, paprika, turmeric, black pepper, cayenne pepper, and cardamom in a small bowl. Sprinkle over chicken and turn to coat evenly.
Melt clarified butter in a large, heavy skillet over high heat. Cook chicken thighs in hot butter until browned on all sides, 5 to 10 minutes. Transfer chicken to a plate. When cool enough to handle, cut chicken into bite-sized pieces.
Make sauce: Place the skillet with chicken drippings over medium-high heat. Stir onion into the skillet; sauté until onion softens and turns translucent, 5 to 6 minutes. Stir in tomato paste and cook until paste caramelizes, about 5 minutes. Stir garlic and ginger into tomato-onion mixture; cook until fragrant, about 1 minute.
Pour crushed tomatoes into the skillet. Bring to a boil while scraping the browned bits of food off of the bottom of the skillet with a wooden spoon. Pour in coconut milk and chicken broth; bring to a simmer, reduce heat to medium-low, and cook, stirring occasionally, until flavors blend and sauce is slightly reduced, about 15 minutes.
Stir chicken and any accumulated juices into sauce. Add cilantro and red pepper flakes; bring to a simmer, reduce heat to medium-low, and cook until chicken is cooked through and tender, 10 to 15 minutes. Season with salt and black pepper.
