Preheat your oven to 325°F and line a mini muffin pan with pastel cupcake liners.
In a large bowl, combine the cake mix, egg whites, milk, oil, sour cream, vanilla, and a few drops of food coloring. Mix on medium speed for about 2 minutes, until smooth and slightly fluffy.
Fill each liner about 2/3 full. Bake for 12–14 minutes, or until a toothpick comes out clean. Let them cool completely before frosting.
For the frosting, beat the butter until smooth and creamy. Add powdered sugar, heavy cream, vanilla, and food coloring. Beat until light, fluffy, and easy to pipe. Add more cream if needed to get that soft, swirly texture.
Pipe or spoon the frosting onto each cupcake, then finish with Easter candy corn and jelly beans on top.