Sauce:
300 g stock
200 g cream
40 g flour
5 g sugar
1 egg yolk
3 tablespoons finely grated horseradish
Salt and pepper, to taste

Cook the meat in boiling water till tender. Allow to cool and cut in slices.

Remove one third of the stock, stir in cream mixed with flour (avoid forming of lumps). Flavour sauce with salt, sugar, stir in raw egg yolk and beat the mixture in a hot water bath till it thickens. Finally, add grated horseradish.

http://www.youtube.com/watch?v=GeyC2KjWNeY