|2 large||red onions, thinly sliced|
|2 large||sweet onions, thinly sliced|
|6 cups||chicken broth|
|2 cups||beef broth|
|1/2 cup||red wine|
|1 tbsp||Worcestershire sauce|
|2 sprigs||fresh parsley|
|1 sprig||fresh thyme leaves|
|1 tbsp||balsamic vinegar|
|freshly ground black pepper|
|4 slices||French bread|
|8 slices||Gruyere or Swiss cheese|
|1/2 cup||mozzarella or Asiago cheese, shredded|
Melt butter over medium-high heat in a large pot.
Stir in salt, red onions and sweet onions. Cook 35 minutes, stirring frequently, until onions are caramelized and almost syrupy.
Mix chicken broth, beef broth, red wine and Worcestershire sauce into pot. Bundle the parsley, thyme, and bay leaf with twine and place in pot. Simmer over medium heat for 20 minutes, stirring occasionally. Remove and discard herbs.
Reduce the heat to low, mix in vinegar and season with salt and pepper. Cover and keep over low heat to stay hot while you prepare the bread.
Preheat oven broiler. Arrange bread slices on a baking sheet and broil 3 minutes, turning once, until well toasted on both sides. Remove from heat.
Arrange 4 large oven safe bowls or crocks on a rimmed baking sheet. Fill each bowl 2/3 full with hot soup. Top each bowl with 1 slice toasted bread, 2 slice Gruyere cheese and 1/4 of the Asiago or mozzarella cheese. Sprinkle a little bit of paprika over the top of each one.
Broil 5 minutes until bubbly and golden brown. Serve immediately!