Combine Cake mix with listed ingredients in a bowl, stirring until evenly mixed. Pour into prepared pan pan, making sure to smooth out the batter until even. Bake about 20 minutes, or until a toothpick inserted near the center comes out clean.
While that cooks, prepare the frosting. (The frosting needs to go on the cake as soon as it comes out of the oven, because it is a quick-setting frosting) In a medium saucepan, add 1/2 butter and brown sugar and bring it to a boil. Once it starts bubbling, add in the 1/4 cup of milk and bring up to a boil, stirring frequently to create an even mixture.
As soon as it starts boiling again, remove the pot from heat and add in the powdered sugar and maple flavoring. Beat with a wooden spoon until it is smooth. If you've timed it right, you should finish with this around the same time as the cake is being pulled from the oven. If it has already set, I stir it rapidly again.
Pour the frosting over the top of the cake and spread it around to cover the entire surface. This will quickly set and harden.