In a large pot, warm 1 tablespoon olive oil over medium heat. Add mushrooms and garlic; sauté 8 minutes, or until mushrooms are browned. Add leek, potatoes, carrots, celery root (or parsnips), thyme and tomato paste. Cook 2 minutes. Add lentils and broth then bring to a boil. Reduce heat to medium-low, cover, and simmer 20-30 minutes, stirring occasionally.Add lager and simmer 10 to 15 minutes, or until thickened, stirring often. Ladle about 1/2 cup of the liquid out into a measuring cup. Add miso to the cup then whisk until smooth. Stir in cabbage and miso mixture then simmer 4 to 5 minutes, until cabbage softens. Season with salt & pepper, as desired (I like about 1/2 to 3/4 teaspoon). Garnish with fresh parsley, serve and enjoy!