Place chicken in a bowl and drizzle vegetable oil over chicken; toss to coat.

Whisk kosher salt, garam masala, ground cumin, ground coriander, smoked paprika, ground turmeric, black pepper, cayenne pepper, and cardamom together in a small bowl. Season chicken with spice mixture 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-size pieces.

Reduce heat under the skillet to medium-high. Stir onion into skillet; saute until onion softens and turns translucent, 5 to 6 minutes. Add tomato paste and stir. Saute until paste caramelizes, about 5 minutes. Stir garlic and ginger into tomato-onion mixture and cook until fragrant, about 1 minute.

Pour the crushed tomatoes into the skillet and 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, any accumulated juices from the chicken, cilantro, and red pepper flakes into tomato mixture; 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.