Easy birthday cup cake

I found this recipe, I forgot from where the source is, but she mention on her blog from cook's country magazine. It is easy to make and delicious,

Ingredients:

3 C. cake flour

1 t. baking powder

1/2 t. baking soda

1 t. salt

4 eggs (large) at room temperature

2 t. vanilla extract

1 1/3 C. sugar

12 T. butter, melted and cooled slightly

1 1/4 c. buttermilk

Preheat oven to 325. Line 2 standard muffin tins with liners.
Whisk first four ingredients in medium bowl.
Whisk eggs & vanilla in large bowl until well mixed.

Add sugar in a steady stream, whisking constantly.Whisk melted butter in gradually. Next add buttermilk.
Add dry ingredients, 1/3 at a time, whisking in between additions until few streaks of flour remain. Stir batter until most lumps are gone, taking care not to over mix.
Fill cupcake liners 2/3 full. Bake with pans side-by-side (middle position of oven) until cupcakes just begin to color and toothpick comes out clean, 18-22 minutes. Cool in pan for 4 minutes. Remove from pan and cool on wire rack for 1 hour.

The original recipe using this frosting but I made it with key lime butter cream this time.

Quick Chocolate Frosting
1 C. Semisweet chocolate chips, melted and cooled slightly

2 1/2 sticks of butter at room temperature

2 3/4 C. confectioners sugar

1/4. C. unsweetened cocoa

2 T. milk

2 t. vanilla

1/8 t. salt
In electric mixer, beat butter until fluffy (about 30 seconds). sugar 1 cup at a time, mix to combine. Add cocoa, raise speed to high and mix for 1 minute. Add melted chocolate, mix to combine. Reduce speed to medium low, add in milk, vanilla, and salt. Increase speed to high and beat until fluffy (about 30 additional seconds).

Key Lime Butter cream:

1 cup unsalted butter

1 cup Crisco

2 teaspoons real vanilla

1/4 teaspoon salt

8 cups powdered sugar

6 tablespoons key lime juice (more if desired for consistency and flavor)

Directions for Key Lime Butter cream:Beat butter and shortening together for about 5 minutes. Beat in vanilla and salt. Add powdered sugar 1 cup at a time alternating with the key lime juice.