Prepare the Bread: Lay your four slices of sourdough on a clean work surface. Spread the softened butter evenly over one side of each slice. This will be the outside of your sandwiches.

Add the Pesto: Flip the bread slices over so the buttered sides are down. On the unbuttered sides, spread 2 tablespoons of basil pesto on two of the slices. These will be the bottom halves of your sandwiches.

Layer the Cheeses: On top of the pesto-covered slices, evenly divide the grated fontina cheese. Next, arrange the mozzarella slices on top of the fontina. Finish with a little sprinkle of black pepper.

Assemble the Sandwiches: Place the remaining two slices of bread on top, butter-side-up, to close the sandwiches. Gently press down.

Cook the First Side: Heat a large non-stick frying pan or skillet over a medium-low heat. Carefully place the sandwiches in the pan. Cook for 4-5 minutes, until the bottom is a deep golden brown and crisp. I find that pressing down gently with a spatula for the first minute helps create an even crust.

Flip and Finish: Carefully flip the sandwiches over. Cook for another 4-5 minutes on the second side, until it's equally golden and the cheese is fully melted, bubbling, and oozing from the sides. If you’re looking for other cheesy, satisfying meals, you might also love my Cheeseburger Lasagna Recipe.

Rest and Serve: Remove the sandwiches from the pan and let them rest on a cutting board for a minute. This allows the cheese to set slightly, making them easier to cut. Slice in half and serve immediately.