Preparation Heat oil in a large wide pot over medium-low heat; add onions and cook, stirring frequently, until translucent, about 20 minutes. Add garlic; cook, stirring frequently, until onions are golden brown and caramelized, about 20 minutes. Add broth and thyme. Bring to a boil; reduce heat and simmer for 20 minutes. Remove from heat. Add bread to pot. Let stand until bread is saturated, about 10 minutes. Discard thyme. Let cool slightly. Working in batches, purée soup in a blender until smooth; strain through a fine-mesh sieve into a large pot. DO AHEAD: Can be made 1 day ahead. Cover and chill. Cook bacon in a medium skillet over medium heat, stirring occasionally, until brown and crispy. Bring soup to a simmer, adding water to thin if needed. Season with salt and pepper. Ladle into bowls; top with cheese and bacon.
Preparation Heat oil in a large wide pot over medium-low heat; add onions and cook, stirring frequently, until translucent, about 20 minutes. Add garlic; cook, stirring frequently, until onions are golden brown and caramelized, about 20 minutes. Add broth and thyme. Bring to a boil; reduce heat and simmer for 20 minutes. Remove from heat. Add bread to pot. Let stand until bread is saturated, about 10 minutes. Discard thyme. Let cool slightly. Working in batches, purée soup in a blender until smooth; strain through a fine-mesh sieve into a large pot. DO AHEAD: Can be made 1 day ahead. Cover and chill. Cook bacon in a medium skillet over medium heat, stirring occasionally, until brown and crispy. Bring soup to a simmer, adding water to thin if needed. Season with salt and pepper. Ladle into bowls; top with cheese and bacon.