INGREDIENTS
•
6 tablespoons butter, divided
•
1 tablespoon olive oil
•
3 pounds medium yellow onions, peeled and thinly sliced
•
1 teaspoon sugar
•
salt
•
1 tablespoon flour
•
8 cups beef stock
•
2 cups dry white wine
•
freshly ground black pepper
•
4 hamburger buns
•
8 slices of provolone cheese