Joining Ribbing End-to-End

I’ve just finished knitting a beautiful cowl (Berroco Origami) and it calls for joining a K3-P3 ribbing end to end to make a circle of it. Any ideas on what would be the best way to do this would be appreciated.

I like mattress stitch to join ribbing and just about anything else I can think of to use it on. There’s a video of the stitch on the Free Videos tab at the top of the page under Tips.