Preheat oven to 350 degrees
In a skillet over medium heat, cook mushrooms until almost all the liquid has evaporated, about 15 minutes, stirring occasionally.
Meanwhile, blend about half the walnuts to almost a powder consistency in a food processor.
In a medium mixing bowl, combine lentils, herbs, walnuts, mushrooms, egg, salt, and pepper. Stir until combined. Refrigerate for at least one hour.
When the mix is ready, form into balls and place on a cookie sheet. Bake for 30 minutes. Serve on spaghetti with marinara sauce and Parmesan cheese.