Preheat oven to 350°F. Line two muffin pans with 16 cupcake liners. Set aside.
In a medium bowl, mix together cake flour, baking powder, baking soda and salt and set aside.
In stand mixer with paddle attachment, beat butter on medium speed until smooth and creamy, about 1 minute. Add vegetable oil and sugar and beat on medium speed for about 2 minutes until creamed together. Beat in eggs and vanilla extract until combined. Add sour cream and beat until combined.
With the mixer on low speed, add the dry ingredients until just combined. With mixer still running on low, slowly pour in milk and beat until just combined. Do not overmix. Fold in sprinkles, but do not overmix as it can bleed the colors.
Fill cupcake liners a little over halfway full. Bake for 14-18 minutes or until a toothpick inserted in the center of a cupcake comes out clean. When cupcakes are done remove immediately from tins and leave on a cooling rack to cool completely before frosting. Top with sprinkles.
In a stand mixer fitted with a whisk attachment, mix butter and sugar. Mix on low speed until blended and then increase speed to medium and beat for about 3 minutes.
Add vanilla extract and heavy cream and continue to beat on medium speed for 1 more minute, adding some more cream if needed for spreading consistency. If using food coloring, add at this point and mix until you reach desired color. Place in fridge until ready to use on cupcakes.
If you don’t have sour cream, you can replace with Greek yogurt.
All refrigerated items should be at room temperature, which helps the batter mix easily and evenly.
You may not realize this but baking powder and baking soda actually expires pretty quickly. Use baking powder that is less than a year old since it has been opened. If you use older baking powder, it won’t be powerful enough to help leaven the cupcakes. You can test it by stirring half a teaspoon of baking powder into a cup of hot water. It will immediately start to fizz and release carbon dioxide gas if it’s still fresh enough to use. Baking soda should be less than six months old and you can use the same test.
Wait until the cupcake batter is completely mixed before folding in the sprinkles as it can bleed the colors.
When adding the batter to the muffin tin, don’t fill more than ⅔ of the way as they do rise.
Allow the cupcakes to completely cool before adding the frosting, otherwise it will melt.