Spread out wax paper on a work surface. Slice the ciabatta in half across the middle. Brush each half with melted butter. Working from the bottom half, spread out the goat cheese in an even layer to the crust.
Arrange the basil leaves on top followed by the slices of mortadella, pepperoni, mozzarella, prosciutto and pancetta.
Add the spinach on top followed by the sundried tomatoes, roasted red peppers, artichoke hearts and sliced shallots.
On the top half of ciabatta, drizzle on the red wine vinegar, and spread on the pesto and mayonnaise in a thin layer. Place on top to create a giant sandwich.
Wrap the entire sandwich in the wax paper and secure in place with twine or tape. Place the weights on top of the sandwich and press for at least 6-8 hours. (TIP: place on a tray to catch any dripping liquid.)
After pressing, the sandwich should be about half of the height it was before. Preheat a panini press with the grilling option. Remove the sandwich from the wax paper and press until golden brown on each side and the mozzarella is melted in the middle – about 25-30 minutes.
ALTERNATIVE COOKING METHOD: Remove from wax paper and wrap in foil – bake at 425 F for 25-30 minutes.
Cool sandwich to room temperature and then chill overnight. The next day, use a serrated knife to cut the ciabatta into individual sandwiches. Wrap in paper and pack in a picnic. Enjoy!