In a large pot, add 1 cup of water, powdered dashi, soy sauce, mirin and bring to a boil. Then add shimeji, shiitake, and enoki mushrooms and let it simmer. Mix 1 tbsp of water with 1 tbsp of potato starch and pour in mixture into the pot to thicken. Pour in 1 beaten egg in a circular motion and turn off heat when egg is cooked. (Don’t mix the egg to avoid a cloudy soup broth). Your ankake sauce is ready!