1 box white cake mix
1 cup flour
1 cup white sugar
¾ teaspoon salt
1 1/3 cup water
2 tablespoons vegetable or canola oil
1 teaspoon vanilla extract
1 cup sour cream
4 large egg whites
7 tablespoons (53 g) all-purpose flour
1 ½ cups (330 g) milk
1 ½ tablespoons pure vanilla extract
1 ½ cups (283 g) salted butter at cool room temperature*
1 ½ cups (297 g) granulated sugar
Pinch of salt
Preheat oven to 325 degrees F. Place cupcake liners in cupcake pans.
In a large bowl, whisk together cake mix, flour, sugar and salt. Add remaining ingredients and beat with a mixer for 2 minutes, or until well blended.
Scoop batter into prepared cupcake liners, filling each about ¾ full. Bake for approximately 18-20 minutes for regular size, 14-16 minutes for minis, and 30-35 minutes for jumbo.
In a small saucepan, whisk flour into milk together over medium-low heat, stirring constantly, until it thickens. It will be the consistency of a thick paste. Make sure that you whisk the flour and milk together well before you begin cooking it to avoid lumps.
Remove from heat and let it cool to room temperature. This step is key. If your mixture is warm, it will melt your butter, and you’ll end up with runny frosting. Stir in vanilla.
While the mixture is cooling, cream the butter, sugar, and salt together until light and fluffy on medium high-high, about 5 minutes. Make sure that you scrape down the sides and really incorporate the butter and sugar to avoid gritty frosting. Then add the completely cooled milk mixture.
Beat it for about 5 more minutes on medium-high to high until it looks like whipped cream. It may look separated at first, so keep beating it until it comes together and looks like a whipped cream.
*Make sure that your butter isn’t too warm! The butter should be at cool room temperature. You want it to dent if you press it.
Also, if you’re using a hand mixer, beat it on high. This recipe works well with a stand mixer because it has the power to really whip the frosting.
When cooking the milk/flour mixture, you don’t want it to look wet. It should be like a thick paste. If it’s wet and runny, your frosting will be too loose.
Please don’t cut the mixing time short! I know it’s tempting, but it’s important to beat the butter and sugar together for the time the recipe calls for to keep it from being gritty. If you cut the mixing times short, you won’t end up with the right texture of frosting.