Preheat the oven to 350 degrees F. Line a cupcake pan with 12 cupcake liners.
In a small mixing bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.
In a large mixing bowl with an electric hand mixer, cream the granulated sugar, unsalted butter, and vegetable oil for a few minutes until light and creamy. Add the egg, sour cream, and vanilla extract and mix until smooth.
Add in half of the flour mixture and mix until mostly combined. Then, pour in the milk and mix. Add the remaining half of the flour mixture and mix until combined and smooth. Fold in the blueberries.
Portion the cupcake batter into the cupcake liners about 3/4 full. Bake the cupcakes for approximately 20 minutes until the tops of the cupcakes spring back when gently touched. Cool the cupcakes in the pan for 2 minutes and then transfer to a wire rack to cool completely.