Pesto, basil, spinach, and 2 kinds of cheese are all gooey and melty on crusty sourdough.
Preheat grill for medium heat and lightly oil the grate.
Spread butter over one side of the bread slices and pesto sauce over the other side.
Place bread, butter side-down on the preheated grill. Place Muenster cheese on 1 slice. Top with spinach and basil. Add provolone cheese. Cover with the other slice of bread, pesto side-down.
Grill until golden brown, 3 to 4 minutes per side. Slice on the diagonal and serve warm.
Per Serving: 499 calories; protein 22.8g; carbohydrates 30.3g; fat 32.2g; cholesterol 73.3mg; sodium 928.2mg.