It seems like a huge amount of onions (I was shocked when reading the recipe for the first time, but put my faith in Julia and tried it anyhow), but once they are cooked down all the way, it ends up being about a cup of super flavorful, caramelized onions.
Quiche Aux Oignons (from Mastering the Art of French Cooking)
2 lbs minces onions (about 7 cups)
3 Tb butter
1 Tb oil
1 1/2 Tb flour
2 eggs or 3 yolks
2/3 cup whipping cream
1 tsp salt
1/8 tsp pepper
Pinch of nutmeg
2 ounces (1/2 cup) grated Swiss cheese
An 8-inch partially cooked pastry shell on a baking sheet, page 146
1 Tb butter cut into pea-sized dots
Cook the onions in a heavy skillet with the oil and butter over very low heat, stirring occasionally until they are extremely tender and a golden yellow. This will take about an hour.
Sprinkle with the flour, mix well, and cook slowly for 2 or 3 minutes. Allow to cool slightly.
Beat the eggs or egg yolks in a mixing bowl with the cream and seasonings until blended. Gradually mix in the onions and half of the cheese. Check seasoning. Pour into tart shell. Spread on the rest of the cheese and distribute the butter over it. Bake in the upper third of preheated oven for 25 to 30 minutes, until quiche has puffed and browned.
... this recipe can also be found at some of my favorite food blog hops