A club sandwich is something you can almost guarantee will be on a menu at any diner across America. While this isn’t a classic club sandwich it is definitely better for it.
Preheat oven broiler to high. Lay slices of prosciutto out on a baking sheet in a single layer. Broil until the prosciutto is crisp, about 3 minutes. Be sure to check on the prosciutto frequently so it does not burn.
Slice the croissants in half lengthwise then spread mayo on the bottom half. Layer with lettuce, followed by the turkey, slices of crispy prosciutto, havarti, tomato, onion, cucumber and avocado.