In a large pot or Dutch oven, heat the olive oil over medium heat. Add the diced onion and minced garlic, and sauté until the onion becomes translucent.
Add the sliced mushrooms to the pot and cook for about 5-7 minutes, or until the mushrooms release their moisture and start to brown.
Pour in the vegetable broth and add the dried thyme, dried rosemary, dried sage, salt, and pepper. Stir well to combine.
Bring the mixture to a boil, then reduce the heat to low. Cover the pot and let it simmer for about 15-20 minutes, allowing the flavors to develop.Remove the pot from the heat and let the soup cool slightly.
Using an immersion blender or a countertop blender, carefully blend the soup until smooth and creamy. If using a countertop blender, blend in batches if necessary.Return the blended soup to the pot and place it back on the stove over low heat.
Stir in the plant-based milk and let the soup heat through for a few minutes, ensuring it doesn't come to a boil.
Taste the soup and adjust the seasoning with salt and pepper, if needed.Ladle the Lenten Mushroom Cream Soup into bowls and garnish with freshly chopped parsley.
Serve the soup hot as a comforting and meatless meal. Pair it with a side of crusty bread or a fresh salad for a complete and satisfying dining experience.