Lemon Curd - cooking recipe

Ingredients

4 large egg yolks
4 1/2 ounces granulated sugar
3 ounces fresh lemon juice
2 ounces unsalted butter, softened and cut into pieces
1 pinch salt
2 teaspoons lemons, zest of, finely grated (optional)

Preparation

In a non-reactive saucepan, whisk yolk and sugar until well combined.
Add remaining ingredients except lemon zest.
Cook over medium-low heat, stirring constantly (Do not whisk), until thickened and you see the first bubble.
DO NOT ALLOW TO BOIL.
Pour through strainer, stir in zest.
chill in refrigerator with plastic wrap pressed on top of curd to prevent skin forming.