Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Cream together the softened butter and granulated sugar in a large bowl until the mixture is light and fluffy, about 2-3 minutes.

Add the egg, lime zest, lime juice, and vanilla extract. Mix until well combined.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add this dry mixture into the wet ingredients, mixing until just combined to avoid overworking the dough.

Fold in the finely chopped mint leaves, distributing them evenly throughout the dough.

Drop spoonfuls of the cookie dough onto the prepared baking sheet, spacing them about 2 inches apart.

Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden. The centers may look slightly underbaked.

Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.

Optional: Once cooled, dust with powdered sugar or drizzle with a light lime glaze for an extra touch.