1. Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius), if not using a grill. Mix the sauce ingredients in a small bowl, and prepare veggies on a separate plate.
2. To assemble: Dip schnitzel cubes into sauce. Thread onto skewer, a few inches from the bottom. Follow with a whole or half red cherry tomato, yellow cherry tomato if available, a piece of onion or a whole or half pearl onion, and a slice of zucchini. Continue the pattern until about two inches from the top. (Thus can be done a few hours before and refrigerated for later use.)
3. When you are ready to bake or grill, pour more barbecue sauce over the skewers if desired. Either bake for 10-15 minutes and then turn over for another 10 minutes, or place on your electric grill and grill from both sides simultaneously for approximately 10 minutes or until chicken is no longer pink and veggies look grilled. Serve over rice or mashed potatoes.
Feel free to just alternate chicken pieces, half cherry tomato, and a chunk of onion. Be creative and use veggies that you like! Also, you can use semi defrosted schnitzel for this. No need to totally deforst. This way you can put the frozen part back if not used.