A deliciously-sweet, lemon-butter filling is sandwiched between lemon shortbread.
To make the filling, first zest the lemon(s) and finely chop the zest even further. Add the lemon zest, salt and butter to a large bowl. Beat with an electric mixer until fluffy.
Next, slowly incorporate the icing sugar in several additions until everything is well blended. Add the salt and mix to evenly combine. The gray salt gives the filling a sweet/savory combo that is fantastic.
The filling can be made a day in advance. Just make sure it is at room temperature before you fill the cookies.
To begin the cookie dough, first zest the lemon(s) and finely chop the zest even further. In a small pot, add the lemon zest and fresh lemon juice and bring to a simmer. Let this reduce to about 2 tablespoons. Once done, pour the mixture into a small bowl and let cool while you measure out the dry ingredients.
Measure out the dry ingredients. Sift together and then set aside.
Using an electric mixer, beat the butter until light and fluffy. Add the sugar and beat until thoroughly combined. Next, beat in the whole eggs, one at a time. Then add the egg yolks, reserved lemon mixture and beat again.
Finally, add the dry ingredients and mix until everything is just blended together (you may need to switch to a wooden spoon at this point).
Cover the dough and let chill for a few hours or overnight in the refrigerator.
Preheat the oven to 375°F or 190°C.
Line a few baking sheets with parchment paper. Set aside.
On a lightly floured counter, roll out one-third of the dough to about 1/4" -inch thickness. Using a 1 1/2" to 2" -inch cookie cutter, cut out rounds (the size is really up to you). In between a few cuts, dip the cutter into a bit of flour to prevent sticking.
Place the rounds onto the baking sheets and bake for about 8 to 12 minutes or until the cookies just start to turn light golden around the edges. For the best results, bake the cookies one tray at a time, as this allows them to cook more evenly. Store the cut, uncooked cookies on the tray in the refrigerator while the others are baking.
Once baked, transfer the cookies to a rack to cool completely. Continue with the remaining dough until all of the cookies are baked.
Spread about 2 teaspoons of the lemon filling onto the flat side of half of the cookies. Spoon the filling in the middle of the cookie or pipe it into the center. Piping will help the filling to spread out more evenly when the cookies are pressed together. It is also faster.
To assemble the cookies, place the flat side of a second cookie onto the filling. Gently press the two cookies together. That’s it!
These cookies make a nice treat for a brunch or afternoon tea. They also make a very nice gift.