Slice a large focaccia in half lengthwise and separate the top from the bottom. Taking a butter knife, spread the mayonnaise in an even layer on the bottom half of the focaccia bread, then add a layer of mortadella and pepperoni.
On top of the pepperoni, add a layer of genoa salami and provolone cheese. Pat dry two large slices of roasted red pepper, then lay flat on top of the cheese.
Sprinkle an even amount of the cabbage on top of the meats and cheese, then add a few spoonfuls of the shallot dressing on top of the cabbage. Add the top layer of the focaccia, then slice into quarters, and serve.
Notes
When slicing the focaccia, remember to use a serrated bread knife so that you have more control over how the knife cuts through the bread.Pat dry the roasted red peppers to alleviate any extra liquid in the sandwich.Spread the shallot vinaigrette evenly across the cabbage for maximum flavor in each bite.