Preheat oven to 350 degrees and line 24 muffins tins
In a large bowl, whisk eggs, oil, milk, water and vanilla
Sift in cake mix and stir in sour cream
Fill cupcake liners ¾ full and then place a teaspoon of Nutella on top of each one
Using a toothpick, swirl the Nutella into the batter
Bake for 14-18 minutes or until the sides spring back (The tops will stay gooey because of the Nutella.)
Remove the cupcakes from the oven and place directly into airtight containers so seal in moisture
Buttercream:
Beat the Nutella and butter for 5 minutes
Add vanilla, then alternate between adding powdered sugar and heavy whipping cream
Taste the buttercream until you reach your desired sweetness
You may need to refrigerate the buttercream before piping it onto cooled cup
Notes
Sift your dry ingredients to avoid clumps and to make the dry ingredients light and easy to mix.
Beat the butter and sugar together for at least 5 minutes until it is light and fluffy and has changed color.
Mix oil and egg together before adding it to the batter. This will give a better "crumb" to your cupcake.
Fill cupcake liners with a scoop to make sure your cupcakes are all the same size.
After removing cupcakes from the pan, allow them to cool and steam in a closed container. This is a great tip for cupcakes and muffins and helps create a softer, moister cupcake or muffin