Preheat your oven to 350°F (175°C) and line a cupcake pan with festive cupcake liners.

In a large mixing bowl, whisk together the dry ingredients: flour, sugar, baking powder, and salt until well combined.

In another bowl, combine the wet ingredients: egg, buttermilk, sour cream, oil, and vanilla extract and mix until smooth.

Pour the wet ingredients into the dry mixture and gently fold until just combined, being careful not to overmix.

Fold in the jimmies or flat sprinkles until evenly distributed throughout the batter.

Fill each cupcake liner about two-thirds full with batter and bake for 18-20 minutes, or until a toothpick comes out clean.

Allow the cupcakes to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

Once cooled, frost the cupcakes with your preferred frosting and add more sprinkles if desired.