Preheat the oven to 350°F / 175°C. Line a muffin tin with 6 parchment liners.
Add the sugar, flour, baking powder, salt and cubed butter to a medium sized mixing bowl. Use a hand mixer or stand mixer fitted with the paddle attachment to beat the mixture together until the butter has completely combined with the dry ingredients and no large lumps remain.
Add the oil, egg white, vanilla, sour cream and milk to the flour mixture. Whisk the ingredients together just until a cohesive batter has formed, then fold in the confetti sprinkles.
Distribute the batter evenly between the six liners. Bake for 15-18 min., or until a toothpick inserted in the center of the cupcakes comes out clean.
Whipped Vanilla Buttercream
In a medium sized mixing bowl, beat the butter with the salt for 1 minute to remove any lumps.
Slowly beat in the powdered sugar until all of it has been used.
Add in the vanilla. With the mixer running, slowly stream in the heavy cream until you have used all of it. Beat for an additional 1-2 minutes, until the mixture is light and fluffy.
Once the cupcakes have cooled to room temperature, frost them and top with additional sprinkles. Serve and enjoy!