How to Make It
Combine coriander seeds, fenugreek seeds, mustard seeds, kalonji, cumin seeds, fennel seeds, and peppercorns in a small skillet.
Cook over medium-high, stirring often, until fragrant, about 2 minutes. Remove from skillet, and cool completely, about 5 minutes. Transfer to a coffee grinder or spice mill, and grind to a fine powder. Transfer to a small bowl; stir in chile powder.
Stir together shredded cheeses, cream cheese, mayonnaise, pimientos, and salt to taste in a medium bowl.
Heat oil in a small skillet over medium until shimmering. Turn off heat, and add 1 tablespoon achari masala. Allow spices to bloom in hot oil, stirring constantly, about 30 seconds. (Keep an eye out at this stage; the spices can burn easily if the oil or pan is too hot.) Remove from skillet, and let cool completely, about 10 minutes. Stir spice-oil mixture into cheese mixture until combined. Cover and refrigerate at least 3 hours or, for best results, up to 8 hours or overnight. Serve with crackers or on toasted naan.