Combine coriander, cumin, and peppercorns in a dry skillet.

Toast over medium heat, stirring constantly, until fragrant (about 3-5 minutes).

Remove from heat and mix in turmeric, mustard, ginger, and cinnamon.

Transfer the mixture to a blender or spice grinder.

Grind at high speed for 1 minute, or until finely powdered.

Let the powder settle for 30 seconds before opening the container.

Strain the powder through a fine-mesh sieve into a clean, dry jar, using a pastry brush to push it through.

Re-grind and strain any larger bits.

Store in a sealed jar away from light for up to 3 months.