Use a 2-tablespoon cookie scoop to portion the dough on your baking sheets. Leave about 2 inches between each scoop. Bake the whoopie pies for 9-10 minutes or until a toothpick inserted into the center comes out clean.
To make the filling, use a stand mixer or handheld mixer to whip together the softened butter and cream cheese. Add the powdered sugar, heavy cream, and vanilla and keep mixing until the frosting is light and fluffy.