Ingredients
Cupcakes:

1/2 cup all purpose flour see note
1/2 teaspoon baking powder
1/8 teaspoon salt
1 large egg
1/4 cup granulated sugar
2 teaspoons pure vanilla extract
4 tablespoons unsalted butter melted and slightly cooled
1/4 cup milk preferably whole or 2% milk

Vanilla Frosting:

3/4 cup powdered sugar
3 tablespoons unsalted butter at room temperature
1/4 teaspoon pure vanilla extract
1-2 teaspoons milk I used whole milk

Instructions For the cupcakes:

Preheat oven to 350°F. Spray 5 muffin cups or place 5 liners in a muffin pan.

In a small bowl, combine flour, baking powder, and salt. Set aside.

In a large bowl, whisk the egg and sugar for about 30 seconds. Add the vanilla extract and melted butter and whisk until well combined.
 Add half the dry ingredients to the wet ingredients and whisk until just combined. Add the milk, and whisk until just combined. Add the remaining dry ingredients and whisk until combined (being careful not to overmix).

Divide the batter evenly between 5 muffin cups (each cup will be between 2/3 and 3/4 full). Bake for 14-16 minutes, until a toothpick inserted into the center of a cupcake comes out clean. Cool completely before frosting.

For the frosting:

Beat powdered sugar and butter until smooth. Add vanilla extract and 1 teaspoon of milk. Beat on medium speed for several minutes, until light and fluffy. If the frosting appears too thick, add an additional teaspoon of milk.
Frost the cupcakes using a butter knife. Top with sprinkles, if desired.

Recipe Notes

Proper flour measuring: Fluff the flour with your measuring cup to lighten it. Scoop the flour and level off with a knife.

This frosting makes enough to spread a moderate layer on top of each cupcake. If you would like a generous amount of frosting, or if you want to pipe the frosting on top of the cupcakes, you can double the frosting.