In a large mixing bowl, combine peanut butter, soy sauce, dark mushroom soy sauce, garlic chili oil, gochugaru, rice vinegar, and sugar. Whisk together until smooth.

Bring a pot of salted water to a boil. Add dry wheat noodles and cook according to package instructions until chewy. Drain and reserve 1/4 cup of noodle water.

Transfer drained noodles into the bowl with sauce mixture. Toss vigorously until noodles are evenly coated.

If sauce is too thick, add reserved noodle water gradually while tossing until desired consistency is reached.

Plate the noodles and garnish with spring onions, coriander, sesame seeds, and a drizzle of sesame oil before serving.