01 -
Preheat oven to 200°C. Line a large baking sheet with parchment paper.
02 -
Generously spread softened butter on one side of each bread slice, ensuring edges are well covered.
03 -
If desired, sprinkle the buttered side of each bread slice with grated Parmesan and press gently to adhere.
04 -
Arrange 4 bread slices, buttered side down, on the prepared baking sheet. Combine cheddar and Gruyère cheeses in a bowl. Evenly distribute the cheese mixture over the bread on the baking sheet. Top with remaining bread slices, buttered side up.
05 -
Place the baking sheet on the bottom oven rack and bake for 4–5 minutes, until the bottoms are golden and cheese is melted.
06 -
Flip each sandwich carefully and continue baking for an additional 2–3 minutes, until both sides are evenly golden and crisp.
07 -
Rest sandwiches for several minutes before cutting in half and serving.