Slice zucchini into 1/4-inch rounds. Let stand until moisture forms on sides. Salt and pepper both sides. Dip in flour, then egg/milk mixture, then in flour again. In a deep frying pan or pot, heat about 2 inches of oil over medium heat. Fry squash until lightly browned on both sides. Drain well on paper towels. Spread toast with mayonnaise and make sandwiches with squash, onions and ham.
Recipe courtesy of Anna Georgantonis-Keah, Austin, TX