PREPARATION:
- Combine first 5 ingredients in small saucepan; bring to a boil over high heat. Cook 3 minutes. Strain mixture through fine-meshed sieve; discard solids.
- Beat egg yolks and salt in top of double boiler with wire whisk; gradually add tarragon mixture, stirring constantly. Add about 1/3 of butter to egg mixture.
- Fill bottom pan of double boiler with water to 1 inch below level of top pan. Bring water just to a boil; reduce heat to low. Place top of double boiler over hot water and cook until butter melts, stirring constantly with wire whisk.
- Add another 1/3 of butter, stirring constantly. As sauce thickens, whisk in remaining butter. Cook until instant-read thermometer inserted into sauce, but not touching bottom of pan, registers 160°F.
