Preheat fry pan on medium heat, add whole peppercorns. Heat whole peppercorns for a few mins until the aroma comes up. Don’t heat them too long – if you burn them they’ll be bitter.
Mix the still heated peppercorns, mustard seed, and coriander seed in a mixing bowl.
Lightly grind the ingredients currently in the mixing bowl in a spice grinder. You want to break up the whole spices but not pulverize them. I use two quick hits on the grinder in batches until the contents of the bowl have been broken up.
Note: You need to break up the peppercorns when they’re still warm. Key to the flavour.
Combine the remaining ingredients with the freshly ground ingredients.
Store in an airtight container in a cool dark place.