Take a small piece of gum paste and wipe your hands and work surface with it to pick up any dust that may stick to your popcorn as you shape them.
Knead the yellow gel food coloring into the gum paste to color it pale yellow. Place the gum paste into a resealable plastic bag. Tear a small piece of the yellow gum paste, roughly the size of a kernel of popcorn, and roll it into a sphere. With a pointed flat-edged fondant tool, use the edge to indent around the bottom of the sphere about 1/3 from the bottom of the sphere (it will look like a snowman with 2 balls). Use your fingers to flatten the bottom ball and make it into a cup it by thinning out the edges over your finger tip. With a medium ball fondant tool, indent the center of the "cup" to create a crater, working along the edge to thin it out, creating a wavy skirt-like bottom. After the center has been hollowed out and an edge has formed that looks like the bottom of a ruffled skirt, dust the inside of the crater with cocoa powder. Coat a thin skewer with shortening and push through the piece of popcorn through the center to create a hole for the string to pass through.
While the popcorn kernel is still on the skewer, take the pointed fondant tool and ball tool again and re-form anything that was smooshed when making the hole. Remove the skewer.
Knot the end of a string (however long you desire in as many pieces). Coat the end of the string in shortening and string the pieces of popcorn. Repeat until all the popcorn are on the string. Knot the other end of the string as you finish.