Place the bacon in a large saucepan, and cook over medium-high heat, stirring occasionally until crisp, about 5 minutes. Stir the onion into the pan; cook until soft, about 5 minutes. Stir in the mushrooms, garlic, pepper, and sage; cook over medium heat until the mushrooms begin to brown, about 10 minutes.
Pour in broth; bring to simmer. Simmer soup for 10 minutes. Reduce heat to low, sprinkle in Cheddar cheese; stir until melted.
