Magnolia Bakery'S Lemon Curd Filling - cooking recipe

Ingredients

12 egg yolks, at room temperature
3 tablespoons lemon zest, grated
1 cup fresh lemon juice
1/2 teaspoon lemon extract
1 1/2 cups sugar
1 cup unsalted butter, cut in small pieces

Preparation

In a medium-size saucepan, whisk the first five ingredients until thoroughly combined.
Get the saucepan on low heat to warm the mixture, and slowly augment the heat to medium. All the while stiring with a wooden spoon or rubber spatula.
Cook for about 20 minutes until thick and bubbly.
Remove from heat and add the butter, one piece at a time, stirring to incorporate.
Place in the refrigerator until firm.
Note: After cooking the mixture for about 5 minutes, it looked curdled so I strained it and then put it in a glass bowl over a pot with water on a high simmer. I cooked it for about 25 more minutes until it was quite thick and coated the back of a spoon. Then I strained it again and added the butter. It was deliciously tart like lemon curd should be.
A sterile mason jar would be perfect for keeping this inches.