How to Make It
Toast coriander seeds, fennel seeds and black peppercorns in a small skillet over medium, shaking pan, until fragrant, 2 to 3 minutes. Let cool, and then grind spices.
Mash butter with salt and ground spices. Roll butter in parchment; freeze until firm.
Grate over hot rice, pumpernickel toast, or sliced duck breasts.