8 half-inch [12‑millimeter] slices hearty white bread, such as French or Italian
4 tablespoons [55 grams] unsalted butter, at room temperature
1/4 cup [60 grams] homemade (recipe below) or store-bought pesto
2 cups [230 grams] shredded smoked Gouda cheese
Spread one side of each slice of bread with butter, then flip over and spread the pesto evenly over the other side of each slice (about ½ tablespoon per slice).
Heat a large nonstick or cast-iron skillet over medium heat.
Place four slices of bread, butter-side down, in the pan. Divide the cheese evenly over the bread, then cover with a lid and cook until the cheese is about three-quarters of the way melted, a few minutes.
Uncover the pan and top the sandwiches with the remaining bread, butter-side up.
Flip and cook, covered, until the cheese is fully melted and the bread is golden brown, a few minutes more. Let cool slightly, then slice the sandwiches in half and serve.
PRO TIP: Most supermarkets with good cheese departments carry smoked Gouda. If you can’t find it, smoked mozzarella or regular Gouda may be substituted. I find the cheese melts better when shredded, but it’s fine to slice it very thinly if you prefer.