Place the roast, beer, French onion soup, beef broth, sliced onion, salt, and pepper in the slow cooker. Cook on low for 7 hours, or on high for 3 ½ hours. Remove the meat and slice or shred.
Slice the bread and spread it with the softened butter on both sides. Add a healthy amount of meat, cooked onions, a slice of your favorite cheese, and freshly chopped parsley. Bake in a 350 F oven until lightly toasted and the cheese has melted.