5 lbs onions, unpeeled
1/2 cup butter (1 stick)
1 1/2 teaspoons black pepper, freshly ground
2 tablespoons paprika
1 bay leaf
7 (16 ounce) cans beef broth, divided (recommended Swanson's)
1 cup dry white wine (optional)
3/4 cup all-purpose flour (such as Wondra) or 3/4 cup instant flour (such as Wondra)
caramel coloring (optional) or Kitchen Bouquet (optional)
2 teaspoons salt
French baguette (optional)
swiss cheese (optional) or gruyere cheese (optional)
Peel onions and slice 1/8 inch thick, preferably in a food processor.
Melt butter in a 6-quart (or larger) stockpot. Add onions; cook, uncovered, over low heat for 1 1/2 hours, stirring occasionally.
(The long cooking time makes the onions mellow and sweet.) Stir in pepper, paprika and bay leaf; saute over low heat 10 minutes more, stirring frequently.
Pour in 6 cans broth and wine. Increase heat and bring to a boil.
Dissolve flour in remaining 1 can broth.
Stir into boiling soup.
Reduce heat and simmer slowly for 2 hours.
Adjust color to a rich brown with caramel coloring, season with salt. Refrigerate overnight. To serve, heat soup in microwave or on stove top.
If desired, pour into ovenproof crocks or bowls.
Top with a slice of bread and a sprinkling of grated cheese. Heat under the broiler until cheese melts and bubbles, about 5 minutes.
Leftover soup can be frozen.