8 tbsp (1 US. stick) unsalted butter, softened at room temperature
1 cup sugar
2 large eggs
2 large egg yolks
1/3 cup plus 4 tbsp. fresh lemon juice
- Beat butter and sugar in a large bowl using an electric mixer. Slowly add the eggs and yolks one at a time, mixing well after each addition. Pour in lemon juice and mix again. Expect the mixture to look curdled, this is normal.
- Cook the mixture over medium heat in a medium-size saucepan until it looks smooth (no longer curdled.) Increase the heat slightly and cook, whisking constantly, until the mixture thickens. Clip a thermometer to the side of the pan and cook until the mixture reaches 170 degrees.
- Remove the curd from the heat. Transfer the curd to a bowl and press plastic wrap on the surface of the lemon curd to keep a skin from forming. Chill the curd in the refrigerator. The curd will thicken further as it cools. Covered tightly, it will keep in the refrigerator for a week and in the freezer for 2 months.