Add the remaining sugar, vanilla and salt. Blend on low to combine.
Scrape the bowl and beater then beat on high for one minute.
Add the peanut butter and mix to combine, scrape bowl.
Add 3 tablespoons of cream and blend on low. Raise the mixer speed to high and beat about 4 minutes.
The icing can be thinned with additional cream, if desired.
If you'd prefer a less fluffy icing for the purposes of frosting a cake with a smooth appearance (An icing with less air bubbles,) the icing can be mixed on low for 4 minutes.
Recipe by Baking With Dan at https://www.bakingwithdan.com/fluffy-peanut-butter-icing/