In microwave safe bowl, combine Nutella & heavy whipping cream. Microwave on high for 30 seconds. Stir. If shiny & smooth, drizzle or pour over cake. If too liquidy or thick, repeat microwave step.
for frosting:
In mixer, combine butter, cream, & vanilla until smooth.
Stir in Nutella over medium speed. Once combined, add in powdered sugar ½ cup at a time. Mix on medium speed until well combined & fluffy.
Top cake with frosting & ganache as desired. Enjoy!