Bring a small pot of water to a boil. Add lotus root slices and blanch for 2-3 minutes. Drain and set aside to cool.
Heat oil in a large wok or saute pan over medium-high heat. Working in batches to avoid crowding, add cleaned, sliced chicken of the woods and sear until golden on all sides. Remove from pan and set aside.
Cut lotus root slices into quarters. Add to pan and stir fry for a minute or two. Return mushroom to the pan, along with onions, dashi, cooking sake, soy sauce, and sugar. Stir to combine.
Bring mixture to a simmer and reduce heat to low. Allow to simmer for 10-15 minutes, or until the liquid has been reduced by about 75%. Remove from heat.
Portion about a cup of cooked rice into bowls. Top with mushroom mixture and any desired toppings (optional).