If you want to make your own Sichuan pepper oil using red peppercorns, put ½ cup of vegetable oil and ¼ cup of Sichuan peppercorns into a small pot and heat them on medium. When the peppercorns start to fizzle, turn the heat to low, and cook, stirring frequently, until the oil takes on the spice's numbing feeling and citrus-like flavor, about 10 minutes. The peppercorns will darken a bit, but don't let them brown or you'll end up with a burnt flavor. Transfer the mixture to a heat-proof container to cool.