1 tablespoon extra virgin olive oil (EVOO)
4 tablespoons butter
4 large onions, thinly sliced
Salt and pepper
1/2 teaspoon ground thyme
1 large fresh bay leaf
1/3 cup dry sherry
1 quart beef stock, veal stock or consommé
1 1/4 pounds sliced roast beef
4 hoagie rolls or 4 10-12-inch lengths of French bread, cut lengthwise
1 pound Gruyère cheese
Heat the EVOO in a large skillet over medium heat. Melt the butter into the EVOO, then add the onions and stir to coat in the butter. Season with salt, pepper, thyme and the bay leaf. Cook the onions, stirring occasionally, until caramel in color, 30-40 minutes, depending on how thinly you sliced them. Deglaze the onions with the sherry and remove the bay leaf; add the stock.
Heat the rolls in a warm oven to crisp them up a bit.
Dip the rolls in the onions and stock to wet and place them on a baking sheet. Dip the meat in the broth and fill the rolls, topping the beef with some onions and draining off most the stock; top the onions with the cheese and sprinkle the cheese across the roll tops as well. Broil the cheese to melt and serve the sandwiches with more broth and a green salad alongside for dipping.