Combine the urad dal, chana dal, fenugreek seeds, cumin seeds, coriander seeds, red chilies, black peppercorns, and mustard seeds, in a small skillet over medium heat until brown, 5 to 10 minutes. Remove from heat and allow to cool completely. Once cooled, mix in the turmeric; transfer mixture in batches to a coffee grinder or spice mill and grind into a powder.