Except it takes an awful lot of butter... probably equal amounts of butter and flour to form the 2 inch diameter balls of beurre mani�. One could use just butter alone since it makes a much smoother sauce with a nice shiny finish... except it, again, takes prodigious amounts of butter. For best results I'd try cornstarch... it works very well without clumping or after taste. Whisk it with equal parts of water and then add it, as needed, to the stock and you have an instant sauce. The secret is no secret, actually, and that's starch... so one could use rice or potatoes, but, of course, both will produce some flavoring, which you would want to avoid with the wine and cream...