Preheat oven to 350 degrees and line a cupcake pan with cupcake liners.
In a medium bowl, combine flour, baking powder, cinnamon and salt. Set aside.
In a stand mixer or in a large bowl and a hand mixer, cream together butter, white sugar and brown sugar for about 4 minutes, until light and fluffy on medium/medium high speed.
Add the egg, mixing well and scraping the sides of the bowl.
In a small bowl or pourable measuring cup, whisk together milk and vanilla. Set aside.
Starting with the dry ingredients, add about ⅓ to the butter mixture and beat until combined.
Add half of the milk and mix well. Continue alternating dry and wet ingredients, ending with the dry ingredients.
Stir in chopped Crazy Go Nuts Sweet & Spicy Walnut Snacks until combined.
Bake for about 16 minutes or until a toothpick inserted in the middle of the cupcake comes out clean.
Let cool in the pan for about 5 minutes and then transfer to a wire rack to cool completely before frosting with the buttercream.
Using a stand mixer or mixing bowl and hand mixer, beat room temperature butter until smooth and fluffy.
Gradually add the powdered sugar, beating until combined.
Add the cinnamon, salt, vanilla and heavy cream and mix until combined, light and fluffy.
Frost cupcakes, top with more Crazy Go Nuts Sweet & Spicy Walnut Snacks and enjoy!