In a small bowl, combine mustard seeds, cumin seeds, turmeric, chili flake, cayenne pepper, salt, and curry powder.
Heat oil in a medium skillet over medium-high heat. When hot, add the small bowl of spices, and cook, stirring until the mustard seeds begin to pop, about 1 minute. Add onion, reduce heat, and cook, stirring very often, until union is tender, about 5 minutes.
Stir in coconut and heavy cream, reduce heat to a simmer, and cook, stirring often, about 3-5 minutes.
Taste and adjust seasoning with salt and freshly ground black pepper.