01 -
Preheat oven to 400°F (200°C). Slice mushrooms into 1/4-inch pieces and thinly slice the sweet onion. Toss both vegetables with 2 tablespoons olive oil, salt, and pepper. Spread evenly on a baking sheet ensuring ample space to prevent steaming.
02 -
Place the baking sheet in the oven and roast the mushrooms and onions until golden brown, approximately 20 to 25 minutes.
03 -
While vegetables roast, shred Gouda cheese evenly. Choose thick-cut bread slices, slicing if necessary, to hold fillings securely without becoming soggy.
04 -
Melt 4 tablespoons unsalted butter in a skillet over medium heat. Brush one side of each bread slice with melted butter to ensure a crisp, golden crust when grilled.
05 -
On the unbuttered side of one bread slice, layer shredded Gouda, then a generous portion of roasted mushrooms and onions, followed by more Gouda. Top with another bread slice, buttered side facing out.
06 -
Place sandwiches in the skillet and cook over medium heat for 3 to 4 minutes per side until the bread is golden-brown and the cheese is melted. Gently press with a spatula to enhance browning and crispness.
07 -
Remove sandwiches from heat, cut in half, and serve immediately to enjoy the creamy cheese and roasted vegetable flavors alongside a perfectly toasted crust.