Add an extra egg than what they call for on the box, replace the oil with melted butter, replace the water with half & half (10 %) cream and add 2 tsp vanilla.
It seems to give you a little more batter. I made 2 - 8 inch rounds and 6 cupcakes out of each mix. In the picture below you can see that 2 of the 8 inch rounds are a bit deeper and 2 more shallow, but that was just for a recipe I was trying.
(I'll freeze the cupcakes for later when I'll be posting a cupcakes and chocolate sauce recipe. Stay tuned.)
Oh and here's a little trick you might not have known about for cutting a cake for layering. Take a length of string, wrap it around the cooled cake where you want it sliced, cross it over and gently pull.
It'll go right through the cake, I find alot easier than a knife,
and you're ready to make your layer cake!
You might like to try:
And here's that cupcakes with chocolate sauce recipe