Put a medium to large saucepan of water on medium-high/high heat to boil.
Heat 1 tablespoon canola oil in a large nonstick skillet over medium-high heat, cook chicken until no longer pink, 4-5 minutes. Remove chicken and put into a bowl.
Add 1 tablespoon canola oil to nonstick skillet; cook snow peas, carrots, and bell pepper until tender, 4-5 minutes, adding garlic and white parts of scallions when about a minute cook time remains.
Cook chow mein noodles according to package directions.
Return chicken (and any juices that are in bowl) to the skillet.
Whisk sauce and pour over chicken and vegetables, cook until thick, 2-3 minutes.
Serve over chow mein noodles. Garnish with scallion tops, if desired.