Put the coriander and mustard seeds in a small skillet and toast over medium heat, swirling the pan, until fragrant. Transfer the seeds to a mortar and pestle or spice grinder, add the peppercorns, and grind until fine. Transfer to a small bowl.
Add the paprika and mustard and stir until well combined. Store in an airtight container in a refrigerator for up to 1 month.