Lemon Drops

1/4 cup (1/2 stick) unsalted butter, room temperature
1 cup sugar, plus more for rolling the cookies
1 large egg
Zest of 2 lemons
2/3 cups all purpose flour
1/4 teaspoon baking soda
Pinch of salt
2 tablespoons finely chopped candied lemon peel 

Heat oven to 350 degrees. Line 2 baking sheets with Silpat nonstick baking mats and set aside. In the bowl of an electric mixer, using the paddle attachment, cream the butter and sugar until light and fluffy, about 3 to 5 minutes, scraping down the sides of the bowl twice. Add egg; mix on high speed to combine. Add zest; mix to combine. 

In a bowl, whisk together flour, baking soda, salt, and finely chopped candied lemon peel; add to butter mixture and mix on medium-low to combine, about 20 seconds. Remove the dough to a sheet of plastic wrap. Chill until firm, about 15 to 20 minutes. 

Pinch off dough and shape into 1-inch balls. Drop the ball in the sugar; using the sugar to keep the dough from sticking to your hands, roll the ball of dough around to coat completely in sugar. Place the cookies on the prepared baking sheet, about 2 inches apart. Press to flatten slightly, the cookies should be about 1/4-inch thick. (Keep the remaining dough in the refrigerator while not in use.) Bake until just golden, about 10 minutes. Remove to a wire rack to cool.