Italian Croque-Monsieur: Pesto and Mozzarella

Ingredients (for 2 servings):

4 slices of white bread (e.g., ciabatta or toast)

2-3 teaspoons green pesto (basil pesto)

100-150g mozzarella (preferably buffalo mozzarella)

2 slices of cooked or air-dried ham (e.g., prosciutto or boiled ham)

2 tablespoons grated Parmesan cheese (optional)

Butter (for spreading)

Fresh basil leaves (for decoration, optional)

Prepare the bread: