In a large pot, bring 2 quartz (or more if using more vegetables) water to boiling.
While waiting for the water to boil, whisk together the 1 ¼ cups of water, peanut butter, soy sauce, brown sugar, cornstarch, crushed red pepper, and 1 of the ramen seasoning packets In a medium sauce pan. (The other seasoning packet can be thrown away or kept another use). The sauce does not have to be whisked until smooth (it will smooth out when cooked).
Cook the sauce over medium heat, stirring frequently, until thickened and bubbly.
Cook for 2 minutes, stirring frequently. Add the chicken, water chestnuts and bamboo shoots to sauce; heat through. (Note: the sauce can remain on the stove, over low heat, until the noodles are ready. Just make sure to stir frequently so the bottom doesn't burn).
When the water in the pot is boiling, add the noodles and vegetables, return to boiling reduce heat. Boil gently, uncovered, for 3 minutes. Drain and return to pot.
Add the sauce mixture to the noodles and vegetable in the pot. Toss to combine.
Serve immediately. Top with peanuts and green onion if desired.