In a small skillet over medium heat, dry roast peppercorns, dehydrated garlic, coriander and mustard seeds until just aromatic or the seeds start to pop. This will take 1-3 minutes, stirring constantly. Immediately transfer into a small bowl so they will not continue to cook and burn. Next, grind roasted spices into a coarse powder using a spice or coffee grinder. Place ground spices into a medium bowl. Add the mayo and yogurt and stir to incorporate the spices thoroughly. Stir in the remaining ingredients until smooth.
Serve cool over salad.