Preheat oven to 325°F. Grease and flour two 9 inch round cake pans and line a cupcake pan with 6 liners (you're going to have 6 cupcakes to munch on along with your cake!)
In a large bowl, whisk together cake mix, flour, sugar and salt. Add remaining ingredients and beat with hand mixer or a whisk for 2 minutes, or until well blended.
Scoop the batter into 6 cupcake liners ¾ full. Divide the remaining batter into the prepared round pans. Bake the cupcakes for about 25 minutes, and bake the cake rounds about 35 to 40 minutes, or until a toothpick inserted in the center comes out clean. Let the cake cool in the pan for 20 minutes, then remove the cake layers to a wire rack to cool completely.
When the cake is cool, you're ready to assemble. Place one layer on a serving plate, and tuck strips of waxed paper underneath the sides of the cake.
Frost the 1st cake layer. Set the 2nd layer on top of the first. Frost the 2nd layer and along the sides of the cake too. Stick Kit Kat's to the sides of the cake, leaving a very small space in between each Kit Kat (¼ inch). Wrap a bow around the cake, securing the Kit Kat's. Fill the top of the cake with M&M's. Pull out the strips of waxed paper and discard. Use any extra frosting to frost your 6 extra cupcakes.
If you refrigerate the cake for a couple of hours or so, it will be much easier to cut and serve. Of course, you'll need to remove the bow just before serving.