This recipe came to me from a friend. She got it from a cake doctor cookbook. A quicker version than scratch and the frosting doesn't have to be cooked in a cast iron skillet. Tastes just as good to me. As you can tell from picture the frosting will harden quickly. Once it starts to harden don't keep tring to spread because it won't move. It's still worth the effort though. I make this one for cake auctions at church. They always bring a large donation.
Place a rack in center oven and preheat to 350*. Generously grease and flour 2 9" cake pans.
Put cake mix, milk, melted butter, eggs, and vanilla in mixer bowl and mix till well combined. Scraping sides down several times.
Divide evenly between your pans. Bake till golden brown and spring back when lightly touched. 27-29 min. Cool 10 min. on rack. Then turn out onto wire rack to cool completely. 30 min. or more.
Meanwhile make your frosting.
Place the butter and brown sugars in a med. size heavy bottom saucepan over med. heat. Stir and cook until mixture comes to a boil, about 2 min.
Add milk and bring back to a boil, then remove from heat. Add powdered sugar and vanilla. Beat with a wooden spoon until the frosting is smooth.
Use quickly (while still warm) to frost your layers as the frosting will harden.
Place one layer right side up on serving platter. Spread the top with warm frosting. Place second layer right side up, on top of first layer, and frost top and sides with clean smooth strokes. Work quickly,as the frosting will set. If the frosting gets too hard to work with, place the pan back over low heat for 1 min. stirring constantly to soften it up.