Bring a large pot of water to a boil, add salt.
Add the whole wheat pasta and cook until al dente, 8 to 10 minutes.
Drain pasta and reserve ¼ cup cooking water.
Briefly rinse pasta under warm running water. Set aside.
In medium bowl whisk peanut butter, reserved pasta cooking water, vinegar, honey, soy sauce, sesame seed oil, ginger, garlic and red pepper flakes until smooth and creamy.
Pour over warm pasta and toss the pasta with chicken, cucumber, red bell pepper.
Sprinkle each serving with scallions and 1 tsp. chopped peanuts.
Serve warm or cold.