Gather all your ingredients and tools. Lay out the slices of white bread on a clean surface.
Using a knife, spread 1 to 2 tablespoons of pesto on one side of each slice of bread. Make sure to cover the entire slice for maximum flavor.
Place a slice of provolone cheese on top of the pesto-covered side of one slice of bread.
Top the cheese with the second slice of bread, pesto side down.
Spread 1 tablespoon of butter (or mayonnaise) on the outer side of the sandwich. This will help achieve a golden, crispy crust.
Place your skillet or griddle over medium heat and allow it to warm up for a minute or two.
Carefully place the sandwich in the skillet, buttered side down. Cook for 3-4 minutes or until golden brown.
Using your spatula, gently flip the sandwich over and cook the other side for another 3-4 minutes. The cheese should be melted, and the bread should be nicely browned.
Once cooked, remove the sandwich from the skillet. Let it cool for a moment, then slice it in half. Serve it warm and enjoy every gooey bite!
