Nantua Sauce

Ingredients

First you have to make a flavoured butter: Take 250g (8oz) of butter
and soften it to room temperature, or beat it to make it pliable.
Using a wooden spoon or pestle work it inot the prepared flavouring
of your choice. Using a flexible scraper press the butter through
a very fine meshed drum sieve. Use the butter immediately of cover
and refrigerate. For Crayfish butter: Poach 250g (8oz) of live
crayfish in a court bouillon for 5 to 10 minutes, then let them
cool in their cooking liquid. Pull of the tail of each crayfish,
shell it and reserve the tail meat for a garnish or main dish.
Place the shells and heads in a mortar and pound them to a creamy
paste. Pass this paste through the medium or coarse disc of a food
mill to remove fragments of shell, then pass this puree through a
fine sieve. Work in the softened butter. Sieve the butter again if
necessary.

Instructions

Make 30cl (0.5pint) of white sauce and stir in 10cl (3.5 fl oz) of cream. Off the heat stir in 40g (1.5oz) of crayfish butter and if you like a garnish of crayfish tails. Serve with poached white fish or use the sauce to make a gratin of crayfish tails. (or lobster of course).