In a mixing bowl combine minced ginger, minced garlic, lemon juice, chopped chicken thighs, and tandoori curry paste; mix until the chicken is evenly coated.
Heat 1 tablespoon butter in a non-stick skillet over medium heat.
Add the marinated chicken to the hot pan and cook 3–4 minutes, stirring occasionally, until the chicken is no longer pink; remove the chicken from the pan and set aside.
Return the pan to medium heat and add 2 tablespoons ghee. Add the sliced onion, garam masala, cumin, and smoked paprika; cook, stirring, until the onion is softened and the spices are fragrant, about 2–3 minutes.
Add the cooked chicken back to the pan, then pour in the crushed canned tomatoes and chicken broth; bring to a gentle simmer.
Simmer the sauce until it starts to thicken, then stir in the heavy cream.
Continue to simmer for 10–12 minutes, stirring occasionally, until the sauce is thickened and the chicken is cooked through. Adjust seasoning if needed and serve.