1. Drain the mushrooms, reserving the soaking water. Pour water through a fine strainer and set aside. Coarsely chop the mushrooms and saute them in the butter.
2. Add the onion and tomato and saute until the onion is clear. Add the sauerkraut, wine, Beef Stock, reserved mushroom water, and pepper, and bring to a simmer.
3. Sprinkle the flour over the top of the sauerkraut and then stir in well. Simmer, covered, stirring occasionally, for 30 minutes.
