Spread the pesto on one side of the bread then Top with provolone. Close the sandwich and press firmly on the top.
In a medium skillet, heat about 1 tablespoon of butter over medium-low heat until just melted.
Place your sandwich in the skillet and spread remaining butter over top of the sandwich.
Cook on each side for about 5-6 minutes on a low heat or until each side is a nice crispy golden brown.