Cream the butter on medium-high until it's creamy and light in color, about 5 minutes.

Add the powdered sugar a few cups at a time, scraping down after each addition and making sure each cup is fully incorporated before adding the next one.

Add the Nutella and beat on med-high for a full minute.

Turn the mixer to low and add the vanilla, milk, and salt.

Mix for another 1-2 minutes, scraping down the bowl and paddle as needed, until smooth and fully incorporated