Now that the sweet potatoes are almost done you can roast the mushrooms. Heat up a non-stick pan to medium heat and cook the mushrooms on each side for 5-10 minutes. If your mushrooms are very thick they need longer time than the thinner ones, and it is important that they are cooked all the way through (but do not burn them!). When they are finished, place them on plates and move on to the sweet potatoes. Check that they are cooked by lightly stabbing them with a fork. If so simply drain them, place in a bowl and roughly mash them. Spread this on top of your mushroom, add on however much alfalfa sprouts you wish and top it off with the sun-dried tomatoes and caramelized walnuts.