Fill a large stockpot 2/3 full with water, and bring to a simmer. Add the potatoes, and let cook until fork-tender.
Drain, then add the butter, Pecorino Romano, milk or cream, and salt & pepper to taste. Mash until mostly smooth (I leave mine somewhat chunky, but thats personal preference).
While the potatoes are cooking, in a covered saucepan, combine the dry lentils with 3 cups of Pacific Foods Organic Beef Broth. Bring to a simmer and let cook until tender (20-25 minutes).
In a large high-walled skillet head the olive oil over medium heat. Add the onion, and cook for one minute before adding the garlic, carrots, and mushrooms.
Cook over medium heat, stirring occasionally, until the mushrooms are cooked through. Your carrots may still be slightly crunchy, but thats ok!
Add the tomato paste, rosemary, oregano, and frozen peas. Stir everything together, then sprinkle the flour over the top of the vegetables. Mix it in and cook for 2 minutes before adding the remaining 1 cup of beef broth, and red wine vinegar.
Bring to a simmer, then mix in the cooked lentils and season everything generously with salt and pepper.
If your pan is oven safe, remove it from the heat and leave everything in the pan. If you need to transfer to an oven-safe casserole dish, do that now.
Spread the mashed potatoes in an even layer over the cooked vegetables, and bake at 375F for 30 minutes, or until the top of the potatoes are beginning to brown. Serve warm!
This nutritional information refers to each serving of the entire recipe and not just the products used as ingredients.