I do want to make a Sauce Raifort - bechamel simmered with white wine, freshly grated horseradish, heavy cream and cayenne - for a steak sauce. I just bought the fresh horseradish last week; I'll try to make it Tuesday.
I find making and using a slurry the easiest. I get no lumps if I pour it in slowly while continously stirring. It's not the best for all things the more I think about it.
PS. TaxL, Thanks for letting me borrow the Julia Child video you were so kind enough to search out. It's useful. She used a "new" patented non-stick pan at one point in the show. heheh. My-my, she used alot of pots. It took me years to learn some of the basic techniques she did, like make sure the meat and veggies are dry before sauteeing so they brown not steam. She is Still refreshing to watch.