Rinse the mushrooms, then slice them.
Add mushrooms to a large soup pot with cooking oil and a pinch of salt and pepper. Cook over medium heat until the mushrooms have released their water and it evaporates.
Add onions, carrots, and celery to the pot along the thyme, sage, and rosemary. Cook until the onions are soft.
Add the lentils and the broth to the pot. Stir until combined. Place a lid on the pot, and turn the heat up to high. Bring the soup up to a boil, then reduce the heat to a medium-low. Let it simmer for about 20 minutes, or until the lentils are tender.
Once the lentils are tender, stir in the coconut milk and lemon juice. Let it simmer for another five minutes.
Add salt and pepper to taste. Enjoy immediately, and refrigerate leftovers within 2 hours.