Whisk together the eggs and vanilla in a separate bowl.
In another medium bowl, mix together flour, baking powder, and salt.
In a large bowl, beat the butter and sugar together until light and pale with a stand mixer or by hand.
Add the dry ingredients ⅓ at a time into the stand mixer bowl, alternating with ⅓ of the milk, mixing between each addition, along with the sour cream.
Mix the batter together until combined.
Using a large batter scoop, scoop the cupcake batter into 12 cupcake liners.
Bake cupcakes for about 18-20 minutes or until a toothpick inserted in the center comes out clean.
Remove from the oven. . Cool completely on a wire rack before icing.
Add the butter to a mixing bowl, and beat it for 5 minutes or until it is light and doubled in size with a stand mixer or by hand.
Add the vanilla, and gradually add the powdered sugar and milk, ½ cup at a time, beating well between each addition.
Add food coloring.
Beat the mixture for another 8-10 minutes.
With a spatula or large serving spoon, scoop buttercream into large piping bags.
Use the round and french jumbo metal tips to frost the cupcakes with the buttercream frosting.
Mermaid Tails and Shells
Put the candy melts into a medium squeeze bottle, and put on the cap.
Bring a large saucepan of water to medium heat, but not boiling, and place the squeeze bottle into the water.
Cover with a lid, and let simmer on medium-low heat.
After the candy melts have melted, take the bottles out and put them upside-down in a cup so that the melts flow to the nozzle, and let cool until cool to the touch.
Fill in the plastic molds of the mermaid tails with the candy melt, taking off the excess candy with an icing spatula, and put in fridge for 10 minutes on a cookie tray.
When set, peel off the mold from the candy.
Place the tails on a cookie sheet, and apply the glitter dust with a brush.
Decorate the finished cupcakes with mermad tails.
To thin out the icing, add in the milk slowly and gradually.
When done with the candy melt, place the bottle on its side in the freezer for 5 minutes. When solid, just squeeze to bottle to break up all of the solidified candy, and empty all of the candy into a plastic bag.
You can make the chocolate tails ahead of the cupcakes, and store them in a plastic bag in the fridge.