French Onion Soup - cooking recipe

Ingredients

1/4 c. unsalted butter (1/2 stick)
3 medium onions, thinly sliced
1 1/2 c. dark beer
2 c. beef stock or canned broth
2 c. chicken stock or canned low salt broth
12 (1/2-inch thick) French bread baguette slices, toasted
6 thin slices Gruyere cheese
Freshly ground Parmesan cheese

Preparation

Melt butter in heavy large pot over medium heat.
Add onions and saute until deep golden brown, stirring occasionally, about 20 minutes.
Add beer.
Cover and cook 5 minutes.
Add both stocks and bring to a boil.
Reduce heat and simmer, uncovered, 30 minutes, stirring occasionally.
Season to taste with salt and pepper.
(Soup can be prepared 1 day ahead; cover and refrigerate. Bring to simmer before continuing.)