1. Begin by heating the butter or olive oil in the large pot over medium heat.

2. Add the diced onion to the pot and sauté until it becomes translucent, which should take about 5 minutes.

3. Add the minced garlic to the pot and continue to sauté everything for another 2 minutes.

4. Increase the heat to medium-high and add the sliced mushrooms to the pot. Cook until they have browned nicely, which should take about 10 minutes.

5. Add the vegetable broth to the pot and bring everything to a simmer.

6. Once simmering, add the fresh spinach leaves to the pot and cook until they wilt and become tender, about 2-3 minutes.

7. Carefully pour the soup into your blender and blend until the soup is smooth.

8. Pour the soup back into the pot and return it to the heat. Stir in the heavy cream or almond milk and season with salt and pepper to taste.

9. Allow the soup to heat through for another 2-3 minutes before serving.

10. Enjoy a hearty bowl of this soup alongside a warm slice of rustic bread brought straight from the ovens of Middle Earth.