Preheat the oven to 350 degrees. Make the cake batter according to the package directions and spread it evenly into a large greased, rimmed sheet cake pan (also called a Jelly Roll pan, should measure about 17 1/2 inches by 13 inches). Bake until the cake is cooked through. You'll start to smell the cake and the cake will spring back when touched lightly, 12 to 15 minutes.

While the cake is cooking, in a small sauce pan heat the butter and milk over medium heat until the butter melts, stirring often. Remove from the heat. Add the powdered sugar to a large bowl (you can also use a stand mixer here) and slowly whisk in the melted butter mixture into the powdered sugar. Stir until well combined and no lumps remain. Add the almond and vanilla extract and stir to combine.

While the cake is still warm (let it sit for maybe 5-7 minutes, you want it hot but not pipping hot), drizzle the icing over the warm cake and then use a spatula to spread it to the edges. If you try to spread too much or go over the same place again and again you are going to pull up the top off the cake and get crumbs in your icing. The goal is to quickly spread it out and move on... too much fussing will just make a mess.

Add the sprinkles while the icing is still warm. The sprinkles will also cover any messes you made if you tried to spread the icing too much.

The cake is great warm, at room temperature, and even the next day. No need to refrigerate over night, sugar is an excellent preservative. I have a plastic lid that fits my sheet cake pan and makes traveling a breeze. I highly recommend a lid for your pan.