In a soup pot, melt butter over medium-high heat. Sauté onion for 10 minutes or until it starts to become golden and soft.
Add garlic, fresh and dried mushrooms, thyme, salt and pepper; then sauté for about 10 minutes or until no liquid remains.
Stir in wine until evaporated, then stir in broth and bring to a simmer. Reduce heat and simmer for 10 minutes.
Meanwhile, preheat oven to 400°F (200°C).
Place bread slices on a baking sheet and top each with a slice of cheese. Toast in oven for about 5 minutes or until cheese is melted.
Ladle soup into bowls and top each with a cheesy bread slice.