Lemon Curd Filling
- 6 large egg yolks
- 1 cup sugar
- 1/2 cup freshly squeezed lemon juice, strained
- 8 tablespoons (1 stick) unsalted butter, cut into small pieces
- Grated zest of 1 lemon
- 2/3 cup heavy cream
- 1 tablespoon confectioners' sugar
Whisk together egg yolks, sugar, and lemon juice in a small, heavy-bottomed saucepan. Cook over low heat, stirring constantly, until mixture coats the back of a spoon, 8 to 10 minutes.
Transfer to a small bowl. Stir in butter, piece by piece. Add lemon zest, and let cool completely. Cover with plastic wrap, and transfer to the refrigerator for 2 to 3 days.
When you need the filling, chill a metal bowl and whisk in the freezer, then use to whip together cream and confectioners' sugar until stiff peaks form. Fold cream mixture into lemon curd; chill in refrigerator for at least 20 minutes before using.