Use a knife to make slits in the duck legs through the fat.
Mix two tablespoons of ground coriander with a tablespoon of kosher salt. Rub the mixture on the duck legs and refrigerate for at least one hour.
Heat a cast iron skillet over medium heat. Add the legs to the pan skin side down. Cook for about ten minutes and flip the legs. Cook for another 5 minutes.
Add the garlic and thyme to the pan. Cook for one minute, spooning the melted fat over the duck legs.
Add the chicken stock and cover the cast iron skillet with foil or a lid. Transfer the pan to the oven.
After 1 1/2 hours, flip the duck legs and baste them with the braising liquid. Cook them for another 1 1/2 hours.
Meanwhile, place the diced sweet potatoes on a sheet pan covered with foil. Add the oil, ginger, brown sugar, salt and black pepper. Toss the sweet potatoes to coat and put them in the oven with the duck. Roast the sweet potatoes until fork tender. Remove from oven.
Once the sweet potatoes have cooled, put them in the food processor with heavy cream and butter. Blend until smooth, and garnish with thyme and black pepper.
Once the duck legs have been braising for 3 hours, remove them from the fat. Allow them to cool slightly while heating the oven to 400 degrees.
Place the duck legs on a foil lined sheet pan. Roast them for about 15 minutes, making sure the skin is deep brown and crispy.
Meanwhile, make the honey balsamic glaze. Heat the reserved duck fat over medium heat and add the balsamic vinegar. Cook the vinegar down for about two minutes, until it has thickened. Stir in the honey, broth, butter, and pepper. Remove from heat.