/4 cup cornstarch, divided
1/2 cup cold water
4 garlic cloves, sliced
2 teaspoons fresh ginger, grated
3 tablespoons packed light brown sugar
2 tablespoons low-sodium soy sauce
1/2 teaspoon red pepper flakes
3/4 lb snow peas, trimmed and halved crosswise
2 large egg whites
1/2 teaspoon coarse salt
1/4 teaspoon black pepper
1 lb boneless, skinless chicken breasts, cut into 1-inch pieces
2 tablespoons vegetable oil