Sometimes, you just want more cake mix. Or, ya know, cake.
Many cake decorators use the White Almond Sour Cream Cake, but I find it makes a dry cake. I am pretty picky about having moist cakes. There are other recipes ( Cake Mix Extender) that add just a little extra batter. Adding extra ingredients changes the texture of a cake mix, making it seem more homemade, and it adds extra volume, so you get higher cakes or more cupcakes.
Cake Mix Extender
Makes 36 cupcakes (one cake mix alone makes 24 cupcakes)
Adapted from hpjmom from the Wilton Forums
1 box cake mix (any flavor) (and everything listed on the box)
1 cup flour
3/4 cup sugar
1/2 cup oil
2/3 cup milk (or water, or other liquid)
1 tsp baking powder
1 tsp flavoring (vanilla, almond, whatever you want)
As with a cake mix, you can put all ingredients into mixer and follow the box instructions.
I put the cake mix and dry ingredients into the mixing bowl, then mix on low for a few seconds to incorporate everything. Add liquid ingredients (include everything in the extender as well as everything on the box.) Mix about 30 seconds until blended, scrape down the sides, and then 2 minutes on medium speed, stopping halfway to scrape the sides.
Note: With a white cake batter, the cupcakes are slightly dry.