Sort ingredients
dabbler
QR Code
Listen
Pdf
In a large skillet over medium-high heat, melt the butter and add the onions. Season with salt and pepper and cook, covered, until softened, which should take about 5 minutes.
Uncover, lower the heat to medium-low and cook, stirring occasionally, until the onions are deep golden brown, which should take about 25 minutes (or longer). If the onions start to dry out, add a splash of water. For a touch of acidity, deglaze the pan with vinegar and let it evaporate.
Combine the grated Gruyère with the caramelized onions. Spoon half the mixture onto each of 2 bread slices, then top with the remaining slices. Press gently to hold everything together.
Wipe out (or wash) the skillet, then melt some butter in the skillet over medium heat. Cook the sandwiches until golden brown on the bottom, about 3 to 4 minutes. Add a little more butter, flip the sandwich and grill until the cheese melts and the bread is perfectly crisp and golden. Serve immediately.