In a large saucepan, add the butter and saute the onions, potato and garlic over medium heat, until soft and brown, burned. This may take 30+ minutes; add 1 tablespoon of honey about 15 minutes in, to help caramelize. Lower the heat if needed.
De-glaze the pan with 2 cups wine. Then add the water, beef base, and bouquet garni. Simmer another 15 minutes, then remove the bouquet garni and puree with an immersion blender. Stir in the balsamic vinegar and cream. Then salt and pepper to taste.
Meanwhile, preheat the oven to 400 degrees F and line a baking sheet with parchment paper. Use a cookie cutter or glass to cut out 8+ circles the size of your serving cups.
Sprinkle the puff pastry rounds with Fontina cheese and bake for 15 minutes, until lightly golden and fluffy. Serve the soup with a cheese pillow on top of each cup.
NOTES: Because this Creamy French Onion Soup Recipe is pureed, don't worry about perfect slices of onion, just chop them roughly.You can use beef stock if you like, but I find using Beef Base allows me to create a stronger beef flavor. Beef Base is highly concentrated beef stock.No immersion blender? You can also use a stand blender, but be careful. Work in small batches, and place a towel over the OPEN vent in the lid. That way the steam can escape, but you don't get sprayed with hot soup.