Toast the whole Sichuan peppercorns in a dry wok or frying pan over medium heat, moving them around to prevent them from burning, for about 10 minutes or until fragrant.
Add the vegetable oil to the wok and reduce the heat to low. Simmer for 10 minutes. Strain the oil into a container and discard the Sichuan peppercorns.
Add the soy sauce, chile oil, sesame oil, vinegar, garlic, ginger, scallions, dried chiles, Sichuan peppercorn powder, and sugar to the spiced oil and mix well. Let the dressing rest for about 15 minutes before using.