Preheat oven to 375 degrees and prepare a deep pie dish.
In a large stock pot saute the mushrooms, carrot, celery, and onion in the olive oil for 5-7 minutes. If using frozen veggies, substitute about 1 1/2 cups mixed frozen veggies. Add the garlic and cook for one more minute.
Add the tomato paste and cook for a minute or two until it darkens in color. Deglaze the pan with the red wine for 3-4 minutes until the alcohol dissipates.
Add the broth, lentils, soy sauce, Worcestershire, Italian seasoning, thyme, rosemary, salt and pepper, and stir to combine. Simmer for 20 minutes until the lentils are soft. Stir in the frozen peas.
Meanwhile, bring the potatoes to a boil in salted water. Boil for about ten minutes until soft. Drain and return to the pot. Add the milk, salt, butter, nutritional yeast, and pepper to taste. Mash with a potato masher.
Place the lentil mixture in the pie dish and top with mashed potatoes. Bake for 20-25 minutes until the potatoes brown and the filling is bubbly.
Let sit for 10 minutes to allow the gravy to thicken slightly. Serve warm with parsley or thyme for garnish. Store leftovers in the fridge for 3-4 days.