béarnaisesauce

bé•ar•naise′ sauce`

(bɛrˈneɪz, -ˈnɛz, ˌbeɪ ər-)

n.
a thick sauce of egg yolks, butter, vinegar, wine, shallots, and tarragon.
[< French, =Béarn district in SW France + -aise, feminine of -ais -ese]