Chicken Tikka Masala

1 tablespoon ground coriander
1 1/2 teaspoons ground cumin
1/2 teaspoon ground cardamom
1/2 teaspoon ground nutmeg
1 1/2 teaspoons paprika
1/2 teaspoon cayenne
1 tablespoon grated peeled fresh ginger (from 1-inch piece)
4 tablespoons (1/2 stick) unsalted butter
1 large white onion, finely chopped
1/2 cup heavy cream or half-and-half
1 1/4 teaspoons kosher salt
1/2 teaspoon freshly ground black pepper
1/2 cup chopped fresh cilantro plus additional sprigs for garnish

https://www.epicurious.com/recipes/food/views/chicken-tikka-masala-51171400q