In a food processor fitted with a steel blade, add the mushrooms and onions. Process, until chopped into very small pieces, scraping down sides as needed.
Add the walnuts to the processor with the onions and mushrooms and pulse 10-15 times, until chopped into very small pieces.
Transfer the mixture to a clean bowl. In the food processor, add the carrot and celery. Process until chopped in very small pieces, then set aside.
In a 4 quart pot, heat the olive oil over medium heat. Add the onion/mushroom/walnut mixture and cook, stirring frequently, until the mixture has steamed off most of the liquid and begins to brown. Keep an eye that it doesn't burn.
Make a space in the middle of the pot and add the garlic. Cook for 1 minute.
Add the white wine and simmer for 2-3 minutes, scraping the bottom of the pot with a spatula to remove all brown bits.
Add the carrot/celery mixture, crushed tomatoes, salt, nutmeg, bay leaf, lentils and water
Cover and simmer for 45 minutes, or until lentils are done to your liking. Stir the pot occasionally and keep an eye on the temperature so it doesn't stick to the bottom of the pot and burn.
Stir in the nutritional yeast and balsamic vinegar, taste and adjust seasoning, and serve!