To build the sandwiches, cut the Cuban bread loaf in half crosswise, then cut each of those pieces in half lengthwise, yielding 4 pieces total. Spread unsalted butter generously on the outside of the bread (top and bottom pieces).
On the cut sides of the bread, spread the mustard mixture you prepared earlier. On two of the bread pieces, layer each with 2 oz. Swiss cheese, 4 oz. deli ham, half of the sliced roast pork, and 4 pickle slices. Top with the remaining 2 oz. Swiss cheese on each, then close with the other bread pieces. Wrap each assembled sandwich tightly in foil.