Make caramel buttercream frosting: beat remaining butter on Medium speed for 3 minutes using a mixer. Add half of the caramel sauce and vanilla extract. Add powdered sugar 1/4 cup at a time until ideal consistency is achieved. (It is possible to thin out the frosting by adding milk, and to thicken the frosting by adding more powdered sugar until desired consistency is achieved.)
TIP: No piping bag? You can use a zip-top bag to fill your cupcakes. Spoon the icing into the bag then snip off one corner-use this as the tip. Easy!