This soup is delicious.  It takes a little while to cook but is well worth it.  

You could probably use just beef broth but splitting it between beef and chicken adds a subtle hint of flavor that makes a difference.  

​Ingredients:

6- 8 large onions, sliced
2 T butter
2 tsp salt
1/4 cup red wine (something you would drink not cheap wine)
2 tsp garlic
2 C chicken broth
4 C beef broth
5 sprigs fresh tyme
1 bay leaf
1 tsp sugar
1 tsp soy sauce
1/4 tsp black pepper
Parmesan cheese, to your liking
6 slices of hearty Italian bread

Instructions:​

1. Put onions, butter and salt in slow cooker and cook on high about 6 hours until browned.  
2. Add wine and garlic, stir and set cooker to high and let sit uncovered 15 minutes (this will allow the alcohol to cook off).
3. Stir in broths, tyme, bay leaf and sugar, let cook about 2 more hours.
4. Remove thyme and bay leaf, add soy sauce and pepper.
5. While soup is cooking for the last 2 hours sprinkle bread with olive oil and toast under broiler until just browned but crunchy.  Flip over and toast the other side.
6. Ladle soup into oven proof bowls add bread and top with cheese, put under broiler until cheese is melted.