Start by lining your baking sheet with parchment paper. With a pencil or marker, trace out 8 triangles, about 2-3 inches on each side. These will act as your "tree" templates, so space them out evenly on the parchment. After that, place a Biscoff Ginger Cookie halfway into each triangle.
Next up, melt your green chocolate wafers. Follow the package instructions for the best results. Usually, a microwave works well—just be sure to stir every 30 seconds so the chocolate doesn’t burn.
Once your chocolate is silky smooth, transfer it into your plastic piping bag. Now, cut off only a very small tip from the piping bag.
Starting from the bottom of each triangle, pipe horizontal lines across, layering them until you reach the top. Don’t be afraid to overlap the layers to ensure the tree is nice and sturdy (so it doesn’t crack when picked up!). While the chocolate is still wet, sprinkle your Christmas sprinkles all over the trees to make them festive.
Once all 8 trees are piped and decorated, allow the chocolate to set.