In a large sauté pan, heat the olive oil over moderately high heat and brown the beef in small batches, transferring the beef to a plate with a slotted spoon or tongs.
Add the butter to the sauté pan and cook the onions over moderate heat, seasoning them with salt and pepper to taste. Stir and sauté until the onions are softened. Add all of the mushrooms and cook, stirring until tender. Sprinkle the flour over the vegetables and blend again, stirring 1 minute. Add the sake and bring the sauce to a boil. Reduce the heat and simmer until almost all of the liquid has evaporated. Add the beef broth and simmer 1 minute. Stir in the sour cream and San-J Gluten Free Tamari, blending gently over low heat.
Return the beef to the skillet and gently simmer, carefully stirring occasionally, until the beef is warmed through, about 3 to 5 minutes. Do not allow the sauce to boil or break down the sour cream due to heat. Add the cilantro and adjust the sauce with salt and pepper as needed. Arrange the noodles on a large serving platter and spoon the beef and sauce over the noodles.