For the Crust
1¼cups/155 grams all-purpose flour
¼cup/50 grams granulated sugar
3tablespoons/25 grams confectioners’ sugar
1teaspoon finely grated lemon zest
¼teaspoon fine sea salt
10tablespoons/142 grams cold unsalted butter, cut into cubes
For the Curd
4 to 6lemons
1½cups/300 grams sugar
2large eggs plus 3 yolks
1½teaspoons/5 grams cornstarch
Pinch of fine sea salt
4tablespoons/57 grams butter
¼cup/60 milliliters fruity extra-virgin olive oil
Confectioners’ sugar and flaky sea salt, for sprinkling
Step 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).
Step 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. Add butter and pulse (or use two knives or your fingers) to cut the butter into the flour until a crumbly dough forms. Press dough into prepared pan and bake until shortbread is pale golden all over, 30 to 35 minutes.
Step 3
While the shortbread is baking, prepare the lemon curd: Grate ½ tablespoon zest from lemons and set aside. Squeeze lemons to yield ¾ cup juice.
Step 4
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. Make sure mixture comes to a boil and stays there for 30 seconds or so; you should see it thicken up before you take it off the heat. But once it boils do not cook for longer than 1 minute or you risk the curd thinning out again. Remove from heat and strain into a bowl. Whisk in butter, olive oil and lemon zest.
Step 5
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. Bake until topping is just set, 10 to 15 minutes more. Allow to cool to room temperature, then refrigerate until cold before cutting into bars. Sprinkle with confectioners’ sugar and flaky sea salt right before serving.