In a medium bowl, combine 2 tablespoons of the soy sauce, 1 tablespoon of the cornstarch, and the garlic and stir to combine. Add the chicken strips and toss to coat.
Put the remaining 1 tablespoon cornstarch in a small bowl and whisk in the remaining 1 tablespoon soy sauce and chicken broth.
In a large nonstick skillet, heat the canola oil over medium-high heat until hot. Add the chicken and stir-fry until no longer pink, 4 to 5 minutes. Add the pepper slices, snow peas, and scallions, and stir-fry for 2 minutes.
Stir the broth mixture, add it to the skillet, and cook, stirring, until the sauce is thickened, 1 to 2 minutes.