It's never been easier to whip up a batch of homemade Vanilla Cupcakes! Quickly coming together in just one bowl, these fluffy cupcakes are the perfect medium for any frosting, including this creamy, not-too-sweet, cooked buttercream.
1 1/2cups(3 sticks) salted butterat room temperature
FOR THE CUPCAKES:
Adjust rack to center position of oven and preheat oven to 350°F. Line muffin pans with 24 cupcake liners.
Set a large sifter or fine mesh sieve over the large bowl of an electric mixer. Measure flour, cornstarch, sugar, baking powder, and salt into sieve and firmly hit the palm of your hand against its side to sift all of the dry ingredients together into the bowl. (If desired, repeat this process a few more times for fluffier cupcakes.)
To the sifted dry ingredients, add the softened butter, sour cream, milk, eggs, and vanilla. Beat at medium speed for about 30 seconds or until smooth. Scrape down the sides of the bowl with a rubber spatula and beat for 15 more seconds.
Evenly divide the batter between the 24 cupcake liners (I find it easiest to do this using a cookie scoop). Bake for 18 to 22 minutes or until cupcakes are light golden and test done with a toothpick inserted in center (mine were perfect at exactly 20 minutes). Cool the cupcakes for a few minutes in the pans before transferring them to a wire rack to finish cooling completely.
FOR THE FROSTING:
Measure out flour into a small pot and gradually whisk in milk until smooth. Blend in sugar. Set pot over low to medium-low heat and use a wire whisk to stir continuously until mixture simmers and thickens (to the consistency of very thick cake batter). This will probably take 8 to 10 minutes. Remove pot from heat and stir in vanilla.
Allow milk/flour mixture to cool for about 10 minutes, stirring occasionally. Transfer to the bowl of an electric mixer. Beat at medium-high speed until smooth and completely cool, about 4 minutes. With the mixer running, add softened butter, two tablespoons at a time, allowing it to become fully incorporated before adding the next two tablespoons. Scrape the sides of the bowl with a rubber spatula and beat for 1 more minute until light and fluffy. Use immediately to frost completely-cooled cupcakes or cakes.
Cornstarch makes the cupcakes fluffy and is added to regular, all-purpose flour in lieu of using cake flour.
When baking, I like to make sure that all of my ingredients are at room temperature. I speed things up when necessary by cutting my butter into small pieces and spreading them out on a plate or cutting board (which softens the butter faster than if the stick was left whole), by very briefly microwaving ingredients like milk or sour cream to take off the chill, and by using a bowl of hot water to warm up the the whole eggs.
Many recipes for this type of frosting instruct you to add sugar at the same time as the butter. However, I found that by cooking the sugar in the milk/flour mixture, any graininess had a chance to dissolve. Also, by beating the milk/flour mixture, any small lumps are smoothed out and the mixture cools down much more quickly than if left to cool in the pot.
Frost your cupcakes using an offset spatula, a knife, or a piping bag. Or, as I did here, scoop the frosting into a gallon-sized plastic baggie, snip off the corner of the bag, and pipe the frosting onto the cupcakes in a spiral, starting from the outside perimeter and working towards the center.