• Start by preheating the oven to 350°F.
• In a small bowl, whisk together the flour, baking powder, and salt. Set aside.
• In a large bowl, beat the softened butter, sugar and vanilla extract until creamy. Pour in the eggs and mix well.
• Mix in dry ingredients in 2 batches, alternating with milk.
• Fold in the pretty blue and pink sprinkles. Mix all ingredients until well combined.
• Place white-colored cupcake liners in the 12-cup cupcake pan and fill the cupcake tins about ⅓ full of batter. 
• Bake for 25 minutes. Check with a toothpick to see if the cake part is baked through. When the cupcakes come out of the oven, let them cool completely.

To make the icing:

• Beat the butter, salt, and powdered sugar on low until it’s all combined. Add vanilla extract and beat on medium-high speed until creamy. About 3 minutes. Beat in milk on medium-high speed for 1 minute, or until fluffy.
• Place ½ cup of the plain icing in a small bowl. Stir in a small amount of blue or pink gel food coloring until the icing is the desired color.
• Keep your cupcakes in the pan and cut a small hole on the top of the cupcake, right in the center. This will be filled with blue or pink icing. I used a Wilton 1A icing tip to punch a hole.
• Fill the hole with the icing and place the portion of the cutout cupcake back over the top.
• Pipe plain icing on top and decorate with sprinkles before serving.