Preheat oven to 350°F/175°C. Line a cupcake pan with 12 liners. Set aside.
In a medium bowl, sift together cake flour, baking powder, baking soda, sugar and salt. Set aside.
In a standing mixer fitted with the paddle attachment, beat together butter and oil on medium speed until combined, and no visible lumps of butter remain. The mixture will look lumpy but it’s fine. Scrape down the sides and bottom of the bowl as necessary. On medium speed, beat in the eggs, one at a time, beating well after each addition. Add vanilla bean paste, vanilla extract and beat until combined.
With the mixer on low speed, add half of the dry ingredients and beat just until combined. Add milk and sour cream and beat until combined. Add the remaining half of the dry ingredients and beat slowly or fold by hand using rubber spatula only until combined. Do not over mix.
Divide the batter evenly between 12 cupcake liners in a cupcake pan, filling them about 3/4 full. Bake for 15-20 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs. Allow cupcakes to sit for 10 minutes, then remove from the pan and allow to cool completely on a wire rack.