8-10 large yellow onions,peeled and sliced
1/2 cup (125 g) unsalted butter
6 (10½ oz (315 ml) each)) cans condensed beef broth
1 ½ teaspoons Worcestershire sauce
3 bay leaves
10 slices toasted French bread
grated Parmesan cheese
Full recipe from : yummly.com
Step 1 : Sauté onions in butter until crisp-tender. Transfer ready onions to slow cooker.
Step 2 : Add beef broth,Worcestershire sauce,and bay leaves. Cover and cook,setting on low for 5-7 hours.
Step 3 : Discard bay leaves. Ladle into deep bowls. Top each slow cooker French onion soup with a slice of bread and grated cheese.