In a pan over medium-low heat, toast the coriander and cumin seeds, stirring often, until the seeds brown slightly (typically 1 to 2 minutes, or until fragrant). Transfer the seeds from the pan to a large bowl and place to the side.
Place the kashmiri chilies in the same pan over medium-low heat. Stirring often, roast the kashmiri until they start to lightly brown, approximately 1 to 2 minutes. Transfer the chilies to the same bowl as the coriander and cumin seeds.
Place the fenugreek seeds in the same pan over medium-low hear and toast them until they are lightly browned, approximately 1 minute (or until fragrant). Transfer the fenugreek seeds to the same large bowl as the other spices.
Place the black peppercorns in the pan and, stirring often, heat the black peppercorns until fragrant - approximately 30 seconds to 1 minute. Transfer the black peppercorns to the spice bowl.
Place the chana dal into the pan over medium-low heat. Roast the chana dal, stirring often, until lightly browned, approximately 2 to 3 minutes. Transfer the chana dal into the spice bowl.
Place the urad dal into the pan over medium-low heat. Toast the urad dal, stirring often until lightly browned, approximately 2 to 3 minutes. Transfer the urad dal into the spice bowl.
Place the curry leaves into the pan over medium-low heat. Stir the leaves until they crisp (or if using dried leaves until they become fragrant). Transfer the leaves to the spice bowl.
Place the mustard seed into the pan over medium-low heat. Heat the seeds until they pop (approximately 1 to 2 minutes), then transfer them to the spice bowl.
Remove the pan from the heat, then add in the hing. Stir until the hing slightly changes color and becomes aromatic. Transfer the hing into the spice bowl.
Add the turmeric to the spice bowl and lightly stir. Allow the spices to fully cool to room temperature before starting the grinding process.
Using a mortar and pestle or spice grinder, grind the spice mix into a fine powder. This will likely take a few rounds. Transfer the powder into a bowl then mix all rounds of grinding to fully incorporate all spices.
Use immediately or transfer the sambar powder into an airtight container and seal for future use.