Instructions

1. For the Cupcakes:
2. Preheat the oven to 350 F.
3. Line two 12-cup muffin tins with cupcake liners and set aside. 
4. Sift together the flour, baking powder, and salt and set aside. 
5. Combine the milk and vanilla in a measuring bowl with a spout and set aside. 
6. Combine the sugar, oil, and eggs in the bowl of a stand mixer fitted with the paddle attachment and beat on medium speed until well combined and slightly thickened. 
7. Mix in the sour cream on medium speed until just combined. 
8. Add half the sifted dry ingredients and mix on low until halfway combined. 
9. Add half the milk and vanilla mixture and mix until just combined. 
10. Add the other half of the flour mixture, beat, then add the rest of the milk mixture, and beat until just combined. Don’t overmix. 
11. Fold in the sprinkles. 
12. Fill 24 cupcake liners three-quarters full and bake for 19 to 21 minutes, or until a pick comes out almost clean and the center springs back slightly. 
13. Cool the cupcakes in the pan for 10 minutes and then transfer to a wire rack to cool completely before frosting. 
14. For the Frosting:
15. In a stand mixer fitted with the paddle attachment, cream the butter.
16. Start with the mixer at its lowest speed, then gradually increase the speed, using a rubber spatula to scrape the bowl as needed, until the butter is light in color, perfectly smooth, and makes a slapping sound as it hits the sides of the bowl.
17. If the butter is soft, this should take only 30 seconds, but if the butter is cool, it can take a couple of minutes.
18. Add the sugar, 1 cup at a time, and mix at the lowest speed until fully incorporated before adding the next cup.
19. When all the sugar has been added, scrape the paddle and the bottom and sides of the bowl.
20. Add the vanilla and salt, and beat at low speed for 15 seconds, then increase the speed to as high as you can without making a mess, and whip the buttercream until the mixture is perfectly smooth, creamy, and light, about 5 minutes.
21. Stop the mixer once or twice to scrape the bowl and paddle, then continue beating.
22. At first the buttercream will appear to soften, then it will stiffen and increase in volume.
23. If using food coloring add in and mix until the color is fully combined.
24. Use right away, or store in an airtight container in the refrigerator.
25. When you’re ready to use it, let the buttercream come to room temperature if possible, then put it back in the stand mixer and use the paddle attachment to beat it until it is creamy and stiff again.
26. Frost cupcakes.
27. Decorate with sprinkles, cookies, and lollipops.