Bring a large pot of water to boil over high heat Add the potatoes and cook for 5 minutes Add the cauliflower and cook for another 5 minutes, or until potatoes are fork-tender While the potatoes and cauliflower are cooking, prepare the sauce by blending the tofu, roasted garlic, nutritional yeast, and cashews in a blender until smooth. Drain the potatoes and cauliflower and return to the pot. Mash the potatoes and cauliflower, adding the sauce a little at a time. If the mixture seems to thin, allow to sit for a few minutes to thicken up. Season with salt and pepper to taste, and serve with gravy and sauteed greens if desired. In a small non-stick or cast iron skillet, cook mushrooms over medium-high heat until cooked and slightly browned. In a small saucepan, melt the vegan butter or oil over medium-low heat. Sprinkle in flour and whisk to combine until smooth, and cook for 1 minute. Add the remaining ingredients, and whisk until slightly thickened, around 5 minutes. Stir in cooked mushrooms, and serve warm over potatoes.