Fit a small saucepan with a candy thermometer. Add vegetable oil and Sichuan peppercorns and heat to 325°.
Turn off heat and add red pepper flakes, sesame seeds, and five-spice powder. Let oil cool completely.
Pork
In a large skillet over medium-high heat, heat vegetable oil.
Add pork, breaking up the meat with a wooden spoon. Cook until meat is deeply golden and crispy, then add hoisin sauce, vinegar, and soy sauce.
Cook until all liquid has evaporated.
Sauce
In a large bowl, whisk to combine all ingredients.
Serving
Cook noodles according to package instructions and add to bowl with the sauce, tossing to coat noodles in the sauce.
Divide noodles between serving dishes and top each with pork. Garnish with cilantro, toasted peanuts, and green onions, and drizzle with more chili oil, if desired
