Chicken:

• 1 1/2 lbs boneless, skinless chicken thighs or breasts (cut into bite-sized pieces)
• 1 cup plain Greek yogurt
• 1 tablespoon lemon juice
• 1 tablespoon grated ginger
• 3 cloves garlic (minced)
• 1 1/2 teaspoons ground cumin
• 1 teaspoon ground coriander
• 1 teaspoon smoked paprika
• 1/2 teaspoon turmeric
• 1/2 teaspoon chili powder
• 1 teaspoon salt
• 1/4 teaspoon black pepper
• 1/2 cup cornstarch (for coating)
• oil for frying

Butter Sauce:

• 3 tablespoons butter
• 1 small onion (finely chopped)
• 2 cloves garlic (minced)
• 1 tablespoon grated ginger
• 1 1/2 teaspoons garam masala
• 1 teaspoon ground cumin
• 1/2 teaspoon chili powder
• 1/2 teaspoon turmeric
• 1/4 teaspoon cinnamon
• 1 1/2 cups tomato purée
• 1/2 cup heavy cream
• 1 teaspoon sugar
• salt to taste