Ingredients:

  • 1 cup unsalted butter, cool but not rock-hard
  • 0.5 cup granulated sugar
  • 1 large egg yolk
  • 1 tsp vanilla extract
  • 1 tbsp fresh lemon zest
  • 2 cups all-purpose flour
  • 2 tbsp cornstarch
  • 0.5 tsp salt
  • 0.5 cup freshly squeezed lemon juice
  • 1 tbsp lemon zest
  • 0.5 cup granulated sugar
  • 3 large egg yolks
  • 4 tbsp cold unsalted butter, cubed

Instructions:

  1. Prepare the Lemon Curd: In a small saucepan over low heat, whisk the lemon juice, 0.5 cup sugar, and 3 egg yolks. Stir constantly until the mixture thickens enough to coat the back of a spoon.
  2. Remove curd from heat and whisk in the 4 tablespoons of cold cubed butter until smooth. Transfer to a bowl, cover with plastic wrap touching the surface, and chill until set.
  3. Cream the Dough: In a large bowl or stand mixer, cream the 1 cup of cool butter and 0.5 cup sugar until smooth but not overly aerated.
  4. Add the egg yolk, vanilla extract, and 1 tablespoon of lemon zest, mixing until just combined.
  5. Sift together the flour, cornstarch, and salt. Gradually add the dry ingredients to the butter mixture, mixing on low speed until a cohesive dough forms.
  6. Shape and Partial Bake: Roll dough into 1-inch balls and place on a parchment-lined baking sheet. Use a 1-teaspoon measuring spoon to press a well into the center of each. Chill the formed dough for 15 minutes.
  7. Bake at 350°F (175°C) for 10 minutes. Remove from oven and gently re-press the centers if they have puffed up.
  8. Fill and Finish: Spoon the chilled lemon curd into each well. Return to the oven for an additional 5 minutes to set the curd and finish browning the cookie edges. Cool completely on a wire rack.