3/4 c  Unsalted butter
5    Large onions; thinly sliced
8 c  Beef broth
1 ts Chicken stock base
White pepper
12 oz Jack cheese
French or sourdough bread*

*Note: Bread should be sliced 1-in. thick. Melt butter in large kettle, add
onions and saute until transparent but not browned. Add beef broth and
chicken stock base. Cover and simmer 2 to 3 hours. Remove from heat and
refrigerate overnight or several hours. Discard chilled surface fat. Reheat
and season to taste with white pepper. Slice cheese into 12 slices. Lightly
toast 12 bread slices and top each with 1 slice Jack cheese. Pour soup into
individual ovenproof serving bowls and top with slice of bread and cheese.
Run bowls under broiler just until cheese bubbles and is soft but not
browned.