Heat 2 tbsp unsalted butter and 1 tbsp olive oil in a large pot over medium heat.

Add 1 medium chopped yellow onion and 3 minced cloves of garlic, sautéing until softened (about 5 minutes).

Stir in 16 oz sliced cremini mushrooms, 1 tsp salt, and 1/2 tsp black pepper. Cook until the mushrooms are browned and tender.

Sprinkle 3 tbsp all-purpose flour over the mixture and cook for 1 minute, stirring constantly.

Gradually pour in 4 cups vegetable broth, stirring constantly to avoid lumps, and bring to a simmer.

Reduce the heat and simmer for 15 minutes. Stir in 1/2 cup heavy cream and 1/4 cup chopped fresh parsley, heating gently.

Ladle hot soup into bowls and top with 1 cup toasted bread croutons.