In a heavy saucepan melt butter with oil, stir in the onions and saute until translucent about 4-5 minutes.
Reduce the heat to low and cover for 15 minutes.
Uncover and sprinkle a pinch of sugar and salt and raise the heat to medium, cook uncovered for another 20 minutes or until you have a deep brown color.
Make the broth.
Pour in the white wine and cook off the alcohol, about 3 minutes.
Then add beef broth, the dried tyme, the bay leaf and bring to a boil. Reduce the heat to low and cover for 20 minutes.
Slice the baguette in 1 1/4 " and toast on each side.
Assemble & finish.
Ladle hot soup in an oven proof bowl, add toasted pieces of baguette, and top with a generous amount of grated cheese. Place in oven under "broil" till golden brown.
If you do not have beef broth on hand, then you can replace it with 2 beef bouillon cubes and water. You may also omit the white wine if you do not have in hand. I often make it without and its still as tasty!
Be careful when removing the bowls from the oven on broil, it will be extremely hot!