Flip two of the pieces over so unbuttered side faces up and top each with Old Cheddar, tomato slices, provolone, bacon.
Spread La Bomba (if using) over the remaining two slices on the unbuttered side and close to make two sandwiches, buttered sides out.
In a large heavy skillet or griddle, arrange sandwiches side by side and cook over medium heat until golden, flip with a spatula and cook the remaining side until golden and the cheese is completely melted and gooey, about 5 minutes per side. Serve hot.
Optional Add-Ins: Add fresh basil leaves when in season.