Begin by creaming the butter, cornstarch, and confectioners sugar together. Use an electric mixer on medium speed for about 3 minutes until the mixture is well-combined and smooth, but not fluffy. You want a creamy consistency that will hold the cookie together.
Next, slowly add the all-purpose flour to the butter mixture. Mix just until well-combined; avoid overmixing. You should have a soft, slightly sticky dough that holds its shape when pressed.
Add in the key lime zest and key lime juice. Beat the mixture until everything is thoroughly mixed. The dough should become aromatic with the fresh scent of lime, and it will also begin to feel a bit softer.
Divide the dough into two equal halves. Roll each half into a log that is about 1 inch in diameter. This helps in achieving uniform slices later on.
Wrap each log tightly in waxed paper and refrigerate for at least 1 hour or until the dough is firm enough to slice. This chilling step is crucial for the cookies to hold their shape during baking.
When you’re ready to bake, preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius). The anticipation of delicious cookies will fill your kitchen!
Slice each log into 1/4 inch thick slices. Arrange these slices on a cookie sheet lined with parchment paper. Make sure to leave some space between each cookie, as they will spread slightly during baking.
Bake the cookies in the preheated oven for about 10 minutes or until they are set but not browned. You’ll want to watch them closely since the cookies will remain pale and won't develop a golden color.
Once baked, remove the cookies from the oven and allow them to cool completely on a wire rack. This cooling step is important to ensure they hold their shape.
To make the frosting, cream together the butter and confectioners sugar until fluffy. Add the key lime zest and key lime juice, mixing well until you have a smooth frosting. Spread this frosting generously over the cooled cookies, making them even more delicious.
