In a large boiler set over medium heat, add the butter, garlic, bay leaf, and onions. Brown over high heat for about 5-8 minutes. Reduce heat to medium-low and continue to cook for around 40 minutes. Make sure you keep checking it and stirring, otherwise you will burn the onions. Once the onions have reduced and caramelized, add the wine and stock. Turn heat to low , cover and let simmer for about 10 to 15 minutes.
Meanwhile, make the croutons. Preheat your oven grill to 180 degrees F. Make diagonal cuts into your baguette. Cut about 2 inch slices. Drizzle them with a small amount of olive oil and place under the oven grill for about 2 minutes per side. Remove from oven.
Arrange 4 oven proof bowl and ladle soup into each bowl. Place a croûton in each bowl and top with grated cheese. Place the 4 bowls on a baking sheet and put back under the grill until the top is golden and bubbly, approximately 5 minutes. Serve immediately when removing from oven.
*A note on times provided: appliances vary, any prep and/or cook times provided are estimates only.