Yield: 4 to 6 wedges
- 3 tablespoons unsalted butter, cut into 12 pieces
- 4 teaspoons granulated sugar
- Scant 1/2 cup all-purpose flour
- 2 teaspoons cornstarch
- Pinch salt
- 2 large egg yolks
- 1/3 cup + 2 teaspoons granulated sugar
- 1-1/2 ounces lemon juice (from 1-2 lemons)
- 1 teaspoon finely grated lemon zest
- Pinch of salt
- 2 tablespoons unsalted butter, softened
- To finish: 2 tablespoons (or more) powdered sugar for dusting the tops of the bars
1. Preheat the oven to 325 degrees.
2. Place the butter and sugar in the bowl of a mini-food processor and process until sugar has dissolved into the butter and the mixture is light and fluffy looking.
3. Stir together the flour, cornstarch and salt. Add half of the flour mixture and pulse once or twice to begin to blend in the flour. Add the rest of the flour and mix until combined. Dough will be very crumbly and look dry but will hold together when you pinch it.
4. Dump the dough into a sealable plastic bag and knead briefly until the dough holds together (you can do this on a board without the bag, but it's much less messy to use the bag). Turn the dough out into a 4-1/2-inch spring form pan or a mini-loaf pan(if using a loaf pan, line the pan with a piece of aluminum foil to make it easier to remove the bars after baking). Press the dough firmly into the pan to form an even layer. If necessary, you can use an offset spatula or the back of a spoon to even it out. Prick the surface of the dough lightly with a fork.
5. Bake for 25 to 30 minutes, or until surface is pale golden and edges are lightly browned.
Meanwhile, make the curd:
1. Choose a small saucepan. Place the egg yolks and sugar in the pan and whisk until well blended.
2. Turn the heat on medium-low under the saucepan and stir in the lemon juice, lemon zest and salt. Cook over medium-low heat, stirring constantly, for a couple of minutes. Stir in the butter, 1 tablespoon at a time, and continue to cook until very thick, glossy and opaque. (You may find that you get a foamy white top layer that doesn't seem to want to blend in. I'm not sure why this happens, but you will need to cook the curd until it disappears, which it should do by the time the mixture is thickened.) When the curd is done, it will look like a very bright, thick Hollandaise sauce.
3. As soon as you reach this point, pour the sauce (now called curd) through a small strainer into a bowl. Press it with the back of a spoon to extract the sauce, but leave the coagulated proteins and zest behind.
To finish the bars:
1. When the shortbread base is baked, turn the oven down to 300 degrees. Let the shortbread cool for a few minutes. Pour the lemon curd over the shortbread and smooth it into an even layer.
2. Return the pan to the oven and bake for 10 minutes. Remove from the oven. Let cool thoroughly and refrigerate for 30 minutes to completely set the curd.
3. Run a thin knife or spatula around the edges of the pan. Carefully open the latch of the spring form pan and remove the dessert. Cut into 4 or 6 wedges.
4. Pour the powdered sugar into a small sieve and dust the tops of the bars. (You may need to repeat if not serving right away.)