Creating your own homemade cream of mushroom soup can be as simple as following these few steps:

1. Sauté the Aromatics: In a large pot, heat butter and olive oil over medium heat. Add the chopped onions and sauté until translucent, about 5 minutes.
2. Add the Garlic: Stir in the minced garlic and cook for another minute until fragrant.
3. Cook the Mushrooms: Add the sliced mushrooms to the pot. Cook for about 10-15 minutes, stirring occasionally, until the mushrooms are soft and have released their moisture.
4. Make the Roux: Sprinkle the flour over the mushrooms. Stir well to coat and cook for about 2 minutes to help eliminate the raw flour taste.
5. Add the Broth: Slowly pour in the vegetable or chicken broth. Stir constantly to incorporate the roux and prevent lumps from forming.
6. Simmer: Bring the mixture to a gentle simmer. Cook for about 15 minutes, allowing flavors to meld together.
7. Blend the Soup: For a creamy texture, use an immersion blender to purée the soup until smooth. Alternatively, you can carefully transfer it to a blender in batches.
8. Incorporate the Cream: Stir in the heavy cream and season with salt and pepper. If desired, add a squeeze of lemon juice for added brightness.
9. Final Heat: Return the pot to low heat and warm the soup for about 5 minutes, being careful not to boil it again.
10. Garnish and Serve: Ladle the hot soup into bowls and garnish with fresh parsley before serving.