Preheat oven to 375 degrees F. Spray a baking sheet with nonstick spray and set it aside. Season chicken with salt and pepper, and place in a bowl with egg substitute. Toss to coat and set aside. Put flour in another bowl. One at a time, use a fork or tongs to transfer chicken "nuggets" to the flour bowl, allowing excess egg substitute to drain back into the egg bowl. Thoroughly coat the chicken with flour and then transfer to the baking sheet. Repeat with the remaining flour and chicken. Bake the chicken in the oven until fully cooked, about 10 minutes. Meanwhile, to make the sauce, combine broth with cornstarch in a nonstick skillet and whisk to dissolve. Set stove to medium-low heat. Add syrup, vinegar, ketchup, soy sauce, sesame oil, and garlic. Mix well. Stirring often, cook until it's thick enough to coat a spoon, 2 to 3 minutes. Remove skillet from heat. Add chicken and toss to coat. Plate and sprinkle with sesame seeds and scallions. If you like, add a sprinkle of red pepper flakes. Eat up!