bearnaise sauce Recipe

put chopped shalotts,vinegar, 1 soupe spoon tarragone in a sauce pan. Let this melt slowlly.
Take out of fire;
Add 4 egg yolk. Put back on very slow fire . Keep on stiring while getting in the butter in small pieces. add at last the remainning chervil and tarragone and salt.
careful this must not boil.