Preheat your oven to 350°F (180°C). Line two cupcake pans with about 16 cupcake liners.

In a large bowl, whisk together the cake flour, granulated sugar, baking powder, baking soda, and salt until combined.

Add the room temperature butter to the dry mixture and beat on medium-low speed for 3 minutes, scraping down the sides occasionally.

In a separate bowl, whisk the eggs, sour cream, vegetable oil, and vanilla extract until smooth.

Add the wet mixture to the flour mixture and beat at medium speed for 30 seconds. Then reduce to low speed and gradually add the whole milk until just incorporated.

Spoon the batter into cupcake liners, filling them just over halfway. Bake for 14 to 16 minutes, or until a toothpick inserted in the center comes out clean. Cool completely on a wire rack.

In a clean mixing bowl, beat the room temperature butter on medium speed for 2 to 3 minutes until light and fluffy.

Add powdered sugar, heavy cream, and vanilla extract and mix on low speed for 1 minute. Scrape the bowl and beat on medium speed for 2 more minutes until smooth and creamy.

If frosting is too thin, add 1-2 cups more powdered sugar. If too thick, add heavy cream gradually until desired consistency is reached.