Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a large bowl, cream together butter and sugar until light and fluffy. Beat in eggs, one at a time, then stir in vanilla. In a separate bowl, sift together flour, baking powder and salt. Gradually stir dry ingredients into the creamed mixture.
Roll dough into 1 inch (2.5 cm) balls and place on prepared baking sheet. Flatten each ball slightly with the tines of a fork. Bake for 15 minutes, or until lightly golden.
Remove cookies from oven and let cool. Spread a thin layer of dulce de leche over each cookie and sprinkle with chopped walnuts. Serve, or store in an airtight container.
Interesting Facts
Dulce de leche is a creamy, caramel-like sauce that is popular in Latin America. It is made from simmering sweetened condensed milk for several hours.
Walnuts are a popular nut in many parts of the world. They are high in protein, omega-3 fatty acids, and antioxidants.
Walnut-shaped cookies are a traditional dessert in many cultures.