Prepare the bread: Spread softened butter on one side of each slice of bread. Make sure to spread the butter all the way to the edges to ensure a crispy finish.

Heat the skillet: Preheat a skillet over low heat.

Assemble the sandwich: Place one slice of bread, buttered side down, onto the skillet. Top with the cheese slices (cheddar, mozzarella, and gouda). Place the other slice of bread on top, buttered side up.

Cook the sandwich: Cook slowly over low heat, being careful not to burn the bread. Cook until the bottom is golden brown and the cheese starts to melt, about 3-4 minutes.

Flip and cook: Carefully flip the sandwich and cook on the other side until golden brown and the cheese is fully melted, about another 3-4 minutes.

Serve: Remove from the skillet, let cool slightly, and cut in half. Serve immediately and enjoy!