These cookies are a lovely pale green and would be excellent as a spring dessert or as part of a Christmas cookie platter. You can make the icing or not, as you prefer. But Hayley's tasters loved the frosting with its subtle rum flavoring!
Zest the lime, reserving the fruit for the icing. Wash and dry the mint and chop it into very small pieces.
Cream the butter and sugar together until fluffy. Add the vanilla, egg, lime zest, and mint and mix well.
Stir in the flour, baking powder, and salt together, and then add this to the butter/sugar mixture and mix on low speed only until combined.
On a sheet of parchment paper, shape the dough into a log, cover with the parchment, and refrigerate for two hours or more.
Preheat oven to 375 degrees (F).
Place a second sheet of parchment on a baking sheet. Slice chilled dough into 1/4-inch slices and transfer to prepared pan.
Bake 10 - 12 minutes, or until bottoms and edges are a light golden brown. Cool on baking sheet for 5 minutes then remove to a wire rack to cool completely.
Mix the powdered sugar with the lime juice and rum. Beat until smooth. Ice the cookies once they are cool.
You can adjust the amounts of lime versus rum to please your palate. And add more sugar if it seems too runny.
If you want a stronger mint flavor, add 1/2 teaspoon mint extract to the dough.
Use the method of lightly spooning flour into a measuring cup and leveling.