In a large bowl, combine sausage, onion mixture, and egg. Mix well. Divide into 16 evenly-sized meatballs. Press each meatball into a zucchini boat, filling the space. Shape the meatball so that it is evenly distributed along the zucchini-boat, for more even cooking. Bake at 400°F until pork is fully cooked. About 45 minutes. If desired (and I recommend it!), remove the stuffed zucchini from the oven and sprinkle crushed pork rinds on top. Return to oven and bake for 5 minutes. Makes 16 4 oz portions (or 5 servings each for CaveBoy and CaveGril).