Boil vinegar, wine, onion, tarragon and peppercorns in small saucepan until liquid
has reduced to 2 tablespoons. Pour liquid through fine sieve. In top of double boiler,
over just simmering water, blend egg yolks and warm water until creamy. Bottom of
double boiler should not touch water.
Melt butter over low heat; add 1/2 teaspoons to yolk mixture, beating well with
a wire whisk after each addition.
Set bottom of pan in a cold water bath if eggs
start to look like scrambled eggs. After some butter has been added, up to 1 teaspoon
of butter can be added at one time. Leave the white residue in bottom of butter
After butter is added, stir in vinegar mixture and salt.