In a large bowl toss the mushrooms with the olive oil, salt, and pepper until well coated. Lay out evenly on a baking sheet or lined tray (shown in photos above).
Place the tray on the smoker, cover, and smoke for approximately 45 minutes. Taste one to see if you like the smoke infusion. Remove from smoker. When cool enough to work with, slice the mushrooms into thin slices.
For the Soup:
In a med-large saucepan add one tablespoon of olive oil and the onions. Cook 5 minutes, until starting to get tender. Add the carrots and celery. Stir together and cook an additional 5 minutes. Add garlic and cook 1 more minute.
Add the vegetable stock, thyme, lentils, bay leaf and the sliced smoked mushrooms. Stir together and simmer 20-30 minutes, until lentils have softened.