Add the grated garlic to a bowl and mix with rice vinegar. Let that sit for 10 minutes.
Next, add the peanut butter, water, doubanjiang, soy sauce, sugar, chili flakes, and coriander, if using. Mix all the sauce ingredients together. The sauce will look grainy at first, but continue stirring the ingredients for 1 to 2 minutes. Let the sauce sit while you cook the noodles. The sauce will thicken some more. (See note 6)
Bring a pot of water to boil. Add the noodles and cook according to package directions. The hand-cut noodles I used took 6 minutes to cook.
Drain the noodles and rinse under cold water thoroughly. I actually prefer the texture of the noodles when I shock them in an ice bath for 1 to 2 minutes before draining. (See note 7)
Transfer the noodles to a large mixing bowl. Pour the sauce over the noodles and toss together. Then, add the chopped basil and toss again. Garnish with sesame seeds, chili flakes, and scallions if you like. Serve the noodles on their own or together with other side dishes. See headnote for suggestions.