-
1
Heat oven to 325 degrees and line a 9-by-9-inch baking pan with enough parchment to hang over two of the sides (to be used as handles later to lift the bars out of the pan).
-
2
To make the shortbread base, pulse together the flour, granulated sugar, confectioners sugar, lemon zest and salt in a food processor, or whisk together in a large bowl.
-
3
Add butter and pulse (or use two knives or your fingers) to cut the butter into the flour until a crumbly dough forms.
-
4
Press dough into prepared pan and bake until shortbread is pale golden all over, 30 to 35 minutes.
-
5
While the shortbread is baking, prepare the lemon curd: Grate 1/2 tablespoon zest from lemons and set aside.
-
6
Squeeze lemons to yield 3/4 cup juice.
-
7
In a small saucepan, whisk together lemon juice, sugar, eggs and yolks, cornstarch and fine sea salt over medium heat until boiling and thickened, 2 to 5 minutes.
-
8
Make sure mixture comes to a boil or the cornstarch wont activate.
-
9
But once it boils do not cook for longer than 1 minute or you risk the curd thinning out again.
-
10
Remove from heat and strain into a bowl.
-
11
Whisk in butter, olive oil and lemon zest.
-
12
When the shortbread is ready, take it out of the oven and carefully pour the lemon curd onto the shortbread base; return the pan to the oven.
-
13
Bake until topping is just set, 10 to 15 minutes more.
-
14
Allow to cool to room temperature, then refrigerate until cold before cutting into bars.
-
15
Sprinkle with confectioners sugar and flaky sea salt right before serving.
