In a large bowl, whisk crouton crumbs and cornstarch. Stir in the soy sauce. Add chicken and toss until completely coated. Cover; refrigerate for at least 30 minutes.
Heat the oil in a large nonstick skillet over medium heat. Add chicken and cook, covered, for 20 to 25 minutes until nice and crispy and cooked through. Turn about 4 or 5 times during cooking to avoid burning. Drain on paper towels.
Serve immediately with additional soy sauce, chopped scallions, cooked rice and steamed sugar snap peas, if desired.