2 tablespoons butter
2 tablespoons vegetable oil
4 large skinless, boneless chicken thighs, cut into bite-sized pieces
1 onion, diced
3 cloves garlic, minced
2 teaspoons curry powder
1 tablespoon curry paste
2 teaspoons tandoori masala
1 teaspoon garam masala
1 (6 ounce) can tomato paste
15 green cardamom pods
1 (14 ounce) can coconut milk
1 cup plain yogurt
salt to taste