Grilled Gruyere and Sweet Onions

The new and improved grilled cheese.

Grilled Gruyere and Sweet Onions
(As found on Smitten Kitchen, adapted from Food & Wine)

makes four sandwiches...

Ingredients:
2 teaspoons extra-virgin olive oil
2 teaspoons unsalted butter
1 large onion, halved and thinly sliced crosswise (4 cups)
salt and freshly ground pepper
8 1/2-inch-thick slices of whole-grain bread (substituted sourdough)
Dijon mustard
8 ounces imported Gruyère cheese, thinly sliced
2 dill pickles, thinly sliced lengthwise

In a deep skillet, melt the butter in the oil. Add the onion, cover and cook over high heat, stirring once or twice, until softened, about 5 minutes. Uncover and cook over moderate heat, stirring occasionally, until the onion is very tender and caramelized, about 25 minutes longer. Add water to the skillet as necessary, 1/4 cup at a time, to prevent the onion from scorching. Season the caramelized onion with salt and pepper.

Arrange the bread on a work surface. Spread a thin layer of mustard on each slice. Top half of the slices with the onion, Gruyère and pickles and close the sandwiches.

Preheat a grill pan or panini press. Grill the sandwiches over low heat until the bread is toasted and the cheese is melted, 5-6 minutes. If using a grill pan, press the sandwiches with a spatula and flip them halfway through. Cut in half and serve right away.