Chocolate Cake: Sift cake mix into a large bowl, then add eggs, oil, milk and sour cream and stir until smooth. Set aside.
Banana Cake: Sift cake mix into a large bowl. Mash bananas using a fork in a small bowl and then add to cake mix. Add eggs, oil, sour cream and vanilla extract and stir until smooth.
Strawberry Frosting: Beat butter for 2 minutes. Add in crushed freeze-dried strawberries. (See a below recipe for more on these awesome berries!.) Slowly add in powdered sugar until you reach your desired consistency. Add in vanilla extract.
You can half each box of cake mix and add only half the ingredients if you only want 20 cupcakes. You can use the extra cry cake mix to flavor butter creams later or Rice Crispy treats!