Soak shiitake mushroom in warm water for about 1-2hours or until soft.
Bring water to boil in a stock pot. Into boiling water, add spinach for 25-30 seconds. Grab with tong and transfer into ice water, soak until leaves are cold. Rinse, drain and squeeze well. Set aside and add pinch of salt. Toss.
Into the same boiling water, add sweet pototo noodles. Boil for about 6min or until soft. Rinse in cold water and let it drain in strainer.
Make meat sauce and marinate meat. Set aside. Squeeze water from mushroom and set aside to stir fry.
Into a large mixing bowl, place the noodles. Cut the noodles with scissors and pour in the noodles seasonings. Toss with gloves on. Taste and adjust the seasoning per your liking, then add sesame oil and give another toss.
Chop veggies and stir fry from lightest color to darkest in order. Add little oil into the pan and stir fry: onion, carrot, red pepper, mushroom and meat last. Add pinch of salt to each vegetable when cooking.
Place all the cooked vegetables and meat on top of noodles, including spinach. Toss well with hand. Add sesame seeds and scallion and toss.
Place into a serving bowl. Serve warm or cold.
To reheat, place on a non-stick skillet and stir fry in medium low heat for few minutes.