1.Turn slow cooker to high and add butter. Add onions, bouillon and thyme the pour wine into slow cooker.
2.Cover and allow to cook 7−8 hours (onions will be soft and dark brown). Pour 2 cans beef consommé and 1 cup water into slow cooker and stir to combine. Cook for 1 hour.
3.Remove thyme stems and test for seasoning. Mix cornstarch and ¼ cup cold water together in small bowl then stir cornstarch mixture into soup. Allow to cook an additional 30 minutes.
4.When ready to serve, preheat oven on broil setting. Arrange individual oven safe bowls on a baking sheet. Ladle soup into bowls, filling to ½” from top. Place a piece of bread on top of each portion of soup and top with shredded cheese. Place under broiler until cheese is melted and bubbly (do not walk away! this will take only about 30 seconds to 1 minute).