In the bowl of an electric mixer, cream the butter and 1 cup confectioners' sugar until light and fluffy.
In a separate bowl, whisk together the flour, baking powder, and salt. Add the dry ingredients to the creamed butter and sugar and mix until combined. Add the vanilla extract and mix until combined.
Add the walnuts and almonds and mix until combined. Refrigerate the dough for at least 1 hour.
Preheat the oven to 350°F. Line a baking sheet with parchment paper.
Roll the dough into 1-inch balls and place on the prepared baking sheet. Bake for 10 minutes, or until golden brown.
Roll the cookies in the extra confectioners' sugar and cool on a wire rack.
Interesting Facts
The Italian name for these cookies is "Baci di Dama", which translates to "Lady's Kiss".
The original recipe called for hazelnuts, but almonds and walnuts are now more commonly used.
These cookies are traditionally served at weddings and special occasions in Italy.