This tutorial from Brenna creates these decorative "barnacles" from papier mache pulp, which she is calling "paper clay". Brenna says: "I used paper clay to make these organic barnacles. These lovely little objects would make stunning tabletop centerpieces, small storage vessels, wall decor, votives . . . the options are endless!" Visit site for homemade paper clay pulp recipe and how-to instructions for barnacles.
Creative Paperclay and the instant papier mache's (such as Fast Mache and Celluclay) would be alternative ready-made products suitable for this project.