1 box white cake mix
1 cup all-purpose flour
1 cup granulated white sugar
3/4 teaspoon salt
1 1/3 cups water
2 tablespoons vegetable or canola oil
1 teaspoon vanilla extract
1 cup sour cream
4 large egg whites
Preheat oven to 325°F. Place cupcake liners in cupcake pans (you’ll need approx. 36).
In a large bowl, whisk together cake mix, flour, sugar and salt. Add remaining ingredients and beat with hand mixer for 2 minutes, or until well blended.
Use ice cream scoop to fill prepared cupcake tins- fill about 3/4 full. Bake about 18 minutes, or until toothpick inserted in center comes out clean.
Cool completely then frost with buttercream frosting.
In a large bowl, with a hand or stand mixer, cream together sugar and butter on low speed. Mix until well blended. Increase speed to medium and beat for another 3 minutes.
Add vanilla and cream and continue to beat on medium speed for 1 minute more, adding more cream if needed for desired spreading/piping consistency.
Scoop into a piping bag and pipe decoratively onto cupcakes, or spread onto cupcakes as desired.