Cut the crust off the length sides of your French Bread. Then cut your French bread slices in half. Butter 1 side of each of those slices and set aside.
Take 1 slice of prosciutto at a time and slice it with a very sharp knife down the center length wise, to create two long strips. You want to use a very sharp knife since prosciutto is fragile.
Space the two strips out about 1/4 centimeter, so there is a bit of a gap as seen above, then place the strip of French bread butter side down in the center of the two strips.
Then place a strip of cheddar cheese on top of the French bread, then a few pieces of diced tomatoes, followed by a strip of smoked gouda, followed by the second strip of French bread with butter side up.