Whisk together all of the lemon curd ingredients except the eggs in a medium saucepan over medium heat, for about ninety seconds.
Beat the egg yolks for about thirty seconds in a bowl. Add about a quarter-cup of the hot lemon mixture, and whisk it into the eggs. Add the egg mixture to the hot lemon mixture. Reduce the heat to low and cook while whisking constantly. Keep going until the mixture is thick and the whisk leaves a trail.
Spoon the curd into a small bowl, then cover with plastic wrap directly on the surface of the curd. Refrigerate. The curd will remain good for two days.
To make the cookies, whisk the flour and baking soda together first in a bowl, and set aside. In a second, larger bowl with an electric mixer, beat the butter, sugar and brown sugar until well combined.
Add the egg, salt, vanilla and lemon extracts to the mixer bowl. Beat until the grittiness is nearly gone. Add the flour mixture from step 4. Stir until the mixture is smooth.
Make the cookie batter into two balls. Refrigerate until chilled.
When the dough is cold and you're ready to bake, preheat the oven to 375 degrees. Coat two baking sheets with butter or parchment paper. Remove one of the dough balls from the refrigerator. Coat a board and a rolling pin with flour, and roll out the dough to about a quarter-inch thick--the more uniform, the better. `
With a cookie cutter (between 1 1/4 and 2 inches in diameter, also coated in flour), cut out as many cookies as possible. As you cut, place them about an inch apart on the cookie sheet. Repeat the process with the other dough ball, and another one made out of the scraps. (Those will be for Dad.)
Bake the cookies at 375 degrees for about eight minutes--until the edges just begin to brown. After four or five minutes, switch the pans and rotate them 180 degrees.
