4tablespoonsunsalted butter, softened or cut into pieces
1pinchsalt
Instructions
Place zest in medium bowl. Suspend strainer over bowl.
In the lower part of a double boiler, bring 1-2 inches of water to a simmer.
Add yolks and sugar to the upper part of the double boiler (not yet on the heat). Beat until well blended. Stir in lemon juice, butter, and salt.
Place upper part of double boiler into lower part. Cook mixture over medium-low heat, stirring constantly, until the mixture is thickened, thickly coats a wooden spoon, but still is liquid enough to pour. Do not allow to boil or it will curdle.
When mixture has thickened (196° F), pour it into the strainer. Press mixture through strainer with the back of a spoon until only a coarse residue remains. Stir mixture and zest together. Allow to cool.
Notes
Adapted from Classic Lemon Curd, The Pie and Pastry Bible, Rose Levy Beranbaum.