Beat butter, cream cheese, and vanilla on low speed until smooth and thoroughly blended, about 1 minute.
Add powdered sugar and apple pie spice, mixing until smooth, about 1 minute, then beat on medium speed 1 minute to lighten the frosting.
Add 2 jars Marshmallow Creme to frosting and mix until smooth.
Refrigerate until mixture has set slightly, about 30 minutes.
Spoon mixture between cookies, approx. 1/4 cup per sandwich.
Refrigerate, covered, until ready to eat.