In a Dutch oven or other large, heavy bottomed pot, melt butter over medium heat. Add onions, a pinch of salt and pepper and bay leaf. Cook, stirring every few minutes, until onions have caramelized to a deep brown (30-45 minutes). Reduce heat if onions begin to burn around the edges. Add wine and cook 2-3 minutes, until reduced by half. Add beef broth, water, thyme, cayenne and cinnamon stick. Reduce heat to low and simmer 30 minutes. Adjust salt and pepper to taste.
Meanwhile, prepare the dumplings. Cut Fondü into ½-inch squares. Have a small bowl of cold water on hand before you begin.
Place a wonton wrapper on work surface. Working quickly, dip your finger in the bowl of water and trace the edge of the dumpling wrapper. Place a square of Fondü in the center. Fold the dumpling wrapper in half so it forms a triangle, pressing to seal the edges. Fold the bottom points of the triangle together so the dumplings resemble tortellini. You can also simply leave them as triangles.
Bring a large pot of salted water to boil. When you are ready to serve the soup, drop dumplings into the boiling water, about 10 at a time. Cook 2 minutes and remove with a slotted spoon or bamboo spider strainer and divide among serving bowls. Divide radicchio among bowls. Ladle soup over the dumplings and radicchio. Serve immediately.
*If radicchio is not available, thinly sliced cabbage would work well as a substitute.