Mix water, salt and sugar together with a whisk until salt and sugar are dissolved. Add shrimp and let it sit in the brine for at least 30 minutes. Longer doesn't hurt. Drain shrimp well and pat dry with a paper towel when ready to cook.
While shrimp is brining, combine all sauce ingredients except cornstarch and water slurry in a small saucepan. Heat over low heat for 30 minutes. Cornstarch/water slurry can be whisked in if sauce isn't thick enough after heating.
Pour canola oil into a large, hot, non-stick skillet over medium high heat. Add onion, red pepper and garlic. Stir-fry for 7 minutes, until veggies are softened. Add asparagus and continue stir-frying for about 5 more minutes. Pour veggies into a large bowl and set aside.
Re-heat skillet over medium high heat. Add additional canola oil if desired. Add drained shrimp and stir-fry until they are pink, about 5 - 7 minutes. Add reserved veggies and noodles and stir well. Pour peanut sauce over everything and combine.