Lemon Lust Bars

This recipe is from the Flour cookbook.  If you like lemony desserts, this one is for you.  The mixture of buttery shortbread and tart creamy lemon curd is amazing. 

Shortbread:
1 cup unsalted butter
6 tablespoons sugar
2 tablespoons powdered sugar
1 egg yolk
1 tsp vanilla extract
1 cup all-purpose flour
1 cup cake flour
1/2 tsp baking powder
1/2 tsp salt

Lemon Curd:
2 cups plus 2 tablespoons fresh lemon juice
1/2 cup unsalted butter
1/4 cup heavy cream
8 eggs
4 egg yolks
2 cups sugar
1 tsp salt
1 tsp vanilla extract

To make the shortbread:
Use a stand mixer fitted with the paddle attachment (or handheld mixer or wooden spoon) to cream together the butter, granulated sugar and confectioners' sugar on medium speed for about 5 minutes until light and fluffy (or 10 minutes if using handheld mixer or spoon).  Stop the mixer a couple of times to scrape down the sides of the bowl with a spatula.  Beat in the egg yolk and vanilla on medium speed for 2-3 minutes, or until thoroughly combined.  Scrape the bowl and paddle again with a spatula to make sure the egg yolk is thoroughly incoroporated.

In a medium bowl, sift together the all-purpose flour, cake flour, baking powder, and salt.  On low speed (or with a spoon), slowly add the flour mixture to the butter-sugar mixture and then mix for about 15 seconds, or until the flour mixture is totally incorporated and the dough is evenly mixed. Stop the mixture and scrape the bowl again to make sure all of the flour mixture is thoroughly incoporated.

Scrape the dough out onto a sheet of plastic wrap and wrap the dough in the plastic wrap, pressing down to form a disk 6-7 inches in diameter and 1 inch thick.  Refrigerate dough for about 30 minutes, or until it has firmed up but is still somewhat pliable (at this point the dough can be kept in the fridge for 5 days).

To make the lemon curd:
While the dough is chilling, in a medium nonreative saucepan, combine the lemon juice, butter and cream.  Place over med-high heat and heat to just below a boil.  Meanwhile, in a medium heatproof bowl, whisk together eggs and egg yolks until blended, then slowly whisk in the granulated sugar until combined.  Remove the lemon juice mixture from the heat and gradually whisk a little of it into the sugar-egg mixture.  Continue whisking the hot liquid into the eggs, a little at a time, until all has been incorporated.

When all of the lemon juice mixture has been incorporated, return the contents of the bowl to the saucepan, and return the saucepan to medium heat.  Cook, stirring continuously with a wooden spoon and making sure to scrape the bottom of the pan frequently to prevent the eggs from scrambling, for 5-8 minutes, or unitl the mixture thickens and coats the spoon thickly.  To test, draw your finger along the back of the spoon, the curd should hold the trail for a second or two before it fills.

Remove the lemon curd from the heat and strain through a mesh sieve into a medium bowl or pitcher.  Whisk in the salt and vanilla.

Position the rack in the center of the oven and heat the oven to 350 degrees F.

Lightly flour the dough disk and two large sheets of parchment paper.  Place the dough between the sheets of parchment, and roll it out into a rectangle 9 x 11" and about 1/4" thick.  Carefully peel off the top sheet of parchment (stick the whole thing in the fridge for a few minutes if the dough is sticky at this time).  Transfer the bottom sheet of parchment with the dough to a 9 x11" baking pan or baking dish with at least 2" high sides.  Press the dough to fit the bottom of the pan, and allow the parchment to come up the sides of the pan.  The dough needs to be about the same thickness all around, but it does not have to be smooth.

Bake for about 20 minutes, or unitl the shortbread is light brown.  Remove from the oven (leaving the oven on), pour the lemon curd on top and smooth the filling evenly over the shortbread with a spatula.

Bake for another 15-20 minutes, or until the curd has set and jiggles like firm Jell-O.  Let cool to room temperature in the pan on a wire rack then refrigerate for at least 4 hours or overnight until the curd has set.  (Cover the pan with plastic wrap)

Gently tug the parchment paper on all sides to loosen the shortbread from the pan, then slide it out onto a cutting board.  Trim the edges of the shortbread, then cut into 9 bars.  The bars can be stored in an airtight container in the fridge for up to 2 days.