Preheat oven to 350°F. Line a cupcake tin with paper liners and set aside.

In a medium bowl, stir together the flour, baking powder, and salt. Set aside.

Cream together the butter and sugar until light and fluffy, about 2 minutes. Add the egg yolks ad vanilla and beat until combined. Stir in the flour mixture alternating between the buttermilk, mixing just until combined after each addition.

In a separate bowl, beat the egg whites on high until stiff peaks form, about 5 minutes or so. Then add to the batter and fold until just combined. Fold in the chocolate and pour into the prepared cupcake tin, filling each about 3/4 of the way up. Bake until golden and a toothpick inserted in the middle comes out clean, about 15 to 18 minutes. Remove from the oven and allow to cool completely on a wire rack.

To make the frosting, beat the butter and sugar until creamy, about 2 minutes. Stir in the vanilla, flour, salt and milk and beat on high until light and fluffy, about 7 minutes. Fold in the chocolate chips. Frost the cooled cupcakes and garnish with the cookie cereal, if using. Serve immediately. Any leftovers can be stored in the fridge, wrapped well with plastic wrap, for up to 2 days. Allow to come to room temperature before serving. Enjoy!