Use a saucepan in which to start the process. Place the butter, oil, onion slices, garlic, thyme and bay leaf into the saucepan and sauté over medium heat 10-15 minutes, until the onions begin to get soft and turn color.
At this time place the ingredients into your Crock Pot, cover with the lid and cook on low heat 5-6 hours.
Then, remove the lid from the Crock Pot, turn the heat to high and cook for about 20-30 minutes. Stir occasionally; this lets the onions turn a nice, dark color.
Add the wine, beef stock, sugar and any seasoning you wish. Cover the Crock Pot again and cook for another 30-45 minutes.
When ready to serve have your oven preheated to 400 degrees and fill your oven-safe serving bowls about 3/4 full. Place the toasted bread on top of the soup, spread the grated Gruyere cheese and melted butter from the original saucepan on top and place the servings into your hot oven for about 15 minutes.
Carefully remove from the oven, and serve a hearty bowl of soup.
Readers with questions or comments for Dave Kessler may write to him in care of this publication.