1-Preheat oven to 350°F (175°C). Line a 12-cup muffin pan with paper liners to ensure easy removal and cleanup.

2-In a medium bowl, sift together flour, baking powder, and salt.

3-Using a mixer, beat butter and sugar on medium-high speed until light and fluffy.

4-Reduce mixer speed to low. Add the egg and beat until incorporated. Add the egg white and vanilla extract; beat until combined.

5-Add dry ingredients in three parts, alternating with milk in two parts (begin and end with flour). Mix each addition just until incorporated, scraping the bowl as needed. Do not overmix.

6-Divide batter evenly among liners, filling each no more than ¾ full.

7-Bake for 18-20 minutes, or until a toothpick inserted in the center comes out clean.

8-Cool cupcakes in the pan on a wire rack for 5 minutes, then transfer cupcakes directly to the rack to cool completely.

9-For the frosting: Beat softened butter on medium-high speed until very light and fluffy, about 10 minutes.

10-Add the room temperature dulce de leche and pinch of salt. Beat until well combined, scraping the bowl. Continue beating until the frosting is light and fluffy. Increase speed to high for the final 2 minutes.

11-If not using immediately, chill the frosting.

12-Assembly: Once cupcakes are completely cool, use a small knife or corer to carve a hole about 1 inch in diameter and depth in the center of each cupcake.

13-Fill each hole with a dollop of dulce de leche.

14-Top each cupcake generously with the prepared dulce de leche frosting. Decorate as desired. A piping bag or a large ziplock bag with a corner snipped off works well for application.