• Preheat oven to 350°F.
• Place chopped walnuts on a parchment-lined baking sheet; bake for 6-7 minutes. Set walnuts aside to cool.
• In the bowl of a countertop mixer fitted with the paddle attachment, cream together the butter and sugar until light and fluffy (2-3 minutes on medium speed).
• In a separate bowl, mix together the cake flour, baking powder, and salt. Add the maple syrup, egg whites, and half of the flour mixture to the mixer bowl. Mix on low speed just until combined.
• Add the remaining flour mixture and mix on low until combined.
• Add milk and mix on low until batter is fully combined. (Note: Don’t forget to scrape down the sides of the bowl with a spatula to ensure the batter is evenly mixed.)
• Fold in ½ cup of the chopped walnuts.
• Line a muffin tin with paper liners; fill each tin approximately 2/3 full.
• Bake at 350°F for 26-28 minutes, or until a toothpick inserted into the center of the cupcake comes out clean.
• Meanwhile, place the remaining ½ cup of walnuts in a food processor or mini-chopper. Pulse several times, or until walnuts are coarsely ground. Set aside to use as garnish once cupcakes have been frosted.

For the Maple Frosting

• In the bowl of a countertop mixer fitted with the paddle attachment, cream together the butter and cream cheese on medium-high speed for 3-4 minutes.
• Add powdered sugar 1 cup at a time; mix on low speed for 30 seconds after each addition.
• Add maple syrup and vanilla extract, and mix on low speed until fully incorporated.
• Increase speed to medium-high and whip for 2-3 minutes, or until frosting is light and fluffy.
• Once cupcakes have cooled, frost as desired. (I used a piping bag fitted with a large round tip.)
• Garnish cupcakes with the remaining chopped walnuts.