Bring a medium pot of water to a boil (about 3 quarts) for the wontons. Meanwhile, in a medium bowl, combine the peanut butter, sugar, soy sauce, sesame paste, sesame oil, rice vinegar, garlic, and white pepper.

Once boiling, stir it to keep the water moving and add the wontons (this prevents the wontons from sticking to the bottom of the pot). Bring the water back up to a simmer. Simmer for 4 to 5 minutes (5 to 6 minutes if frozen), or until the wontons float. If the water comes back up to a vigorous boil during this process, add ¼ cup cold water to cool down the pot. (This periodic addition of cold water prevents the wrappers from overcooking before the filling cooks through.)

Once the wontons are floating, cook them for 1 additional minute. Add ¼ cup of the wonton cooking water to your sauce mixture, and stir until smooth. Once the wontons are finished cooking, use a spider strainer or slotted spoon to lift them out of the water and transfer them to a large bowl.

Pour the sauce onto the wontons, and gently toss them in the sauce. Add additional cooking water 1 tablespoon at a time if the sauce is too thick.

Transfer to a serving dish and top with the chopped scallion and peanuts. If you like your wontons a little spicy, drizzle the chili oil over the top.