will foam up and then fall down.) Watch closely for
small brown flecks. As soon as you see these flecks,
remove the saucepan from the heat and whisk the
butter vigorously. You don’t want the specks to turn
black—that means it’s turned into black butter (which
is common in French cuisine, but it just tastes burnt to
me).
- Add the tarragon, shallot, and vinegar to the
browned butter and place over medium heat. Simmer
for 15 minutes. Remove the pan from the heat and
allow the sauce to cool a bit. - Place the egg yolks in a blender and turn it to low
speed. Slowly pour in the warm (not hot) browned
butter mixture in a very slow, steady stream while the
blender is running. If you do it too fast, the sauce will
break. Taste the sauce and add salt to your liking. Set
aside at the back of the stove or other warm spot to
keep warm until ready to serve. - Store extras in an airtight container in the
refrigerator for up to 3 days. Reheat in a double boiler,
heating it gently so the sauce doesn’t separate.