In a pre-heated 450 degree oven, bake yams on sheet pan, skin on for about 45 minutes or until easily pierced with a fork. Cool long enough that you can handle them, peel off skin, put the insides in a stand mixer with “butter” and milk, whip till light and fluffy, turn down speed add truffle oil. Season with salt and pepper and set aside.
Cook lentils in four cups water for about 20 minutes, until tender but not mushy. Drain, set aside.
In a large bowl combine all the veggies for the filling except mushrooms and yellow onion. Sprinkle with salt and pepper and olive oil, spread evenly onto two sheet pans and roast in oven at same temp as the yams or sweet potatoes cooked for about 25 minutes.
In a medium saucepan add a bit of olive oil, over medium heat add diced yellow onions, and fresh mushrooms cook down over medium heat for 15 minutes or so. Add tomatoes, porcini, miso, braggs, or soy cook 10 more minutes, deglaze with wine, reduce by half, add stock, season with salt and pepper. Cook 20 minutes and then blend together, with a blender or an immersion blender is what I used, doing this sort of naturally thickens your sauce without having to add any additional thickeners.
In a 3 quart casserole dish place cooked lentils, top with roasted veg, sprinkle with fresh herbs, and spoon over the sauce, paying close attention to every nook and cranny. Top with yams and bake 30 minutes or so on the same temp till bubbly and browned. Garnish with more herbs if needed. Let sit at least 15 minutes before feasting.