Walter was a chef at the prominent German restaurant in Ottawa. He was also a neighboor and a good friend of our family. I had a chance and good fortune to cook with him a few times, just for fun, and picked up some interesting shortcuts i still use occasionally. Here is one.
Horseradish sauce served at the restaurant with Prime Rib roast, or with Beef Tongue, was made simply with slices of toasting bread dilutted slowely in hot milk. To this thick redeisue you add a lot of fres or prepared grated horseradish. Cook it gently over the low heat, then add some lemon juice, salt, and masses of pepper.
If too thick, dilute with some decent beef broth, or more milk. If you feel like it, you can also add a spoonfull or two of sour cream, but i find it not necessary.
This is a much heavier sauce than the one here, but very much in line of traditional taste. Some like it the most..