Slow-Cooker Duck Pho features delicious, rich, broth accented by bright, fresh herbs. A great use of leftover roast duck.
Place duck carcass into slow-cooker with remaining duck stock ingredients. Add enough water to mostly cover the carcass (don't overfill your slow-cooker, though!). Set slow-cooker on low for a minimum of 12 hours and up to 36.
Fish out chicken bones and any large solids with a skimmer; place into a colander set inside a bowl. Rinse the solids with approximately 3 cups of cold water. Remove colander and discard solids. Add the liquid in the bowl to the slow-cooker.
Working in batches, strain the stock through a fine-mesh strainer into a degreaser. If you plan to refrigerate the stock before making the soup, pour the degreased stock into a storage container, cool, and refrigerate up to 3 days. If you are proceeding directly to making the soup, pour the degreased stock into a stockpot.
Heat the degreased duck stock in a stockpot with the sliced onions, shiitake mushrooms, and cilantro stems. Simmer for 30 minutes.
Meanwhile, prepare the garnishes and bring the water for the pho noodles to a boil. Cook the noodles according to package instructions. Drain and rinse with cold water.
Mix the ingredients for the nuoc cham in a jar (see Recipe Note #2). Shake to combine.
5–8 minutes before serving, add the roasted duck meat to the simmering broth to heat through. Serve soup with noodles and garnishes to taste.