Heat oven to 400° F. Slice the bread lengthwise. Generously butter one side, and spread mustard to taste on the other.
Over the buttered half, layer on the meats, cheese and pickles. Top with the mustard-coated bread.
Slice the loaf in half to make 2 sandwiches. Wrap each sandwich tightly in aluminum foil.
Place sandwiches in a large cast-iron skillet and weight them down with another cast-iron skillet, or other heavy, oven-proof pan. Bake until the cheese melts, about 20 minutes.
Unwrap and serve (careful: they're hot!).