1. Preheat oven to 325 degrees Fahrenheit (170 degrees Celsius).
2. Let cool to room temperature or refrigerate overnight. Remove the meat onto a cutting board and slice thinly with a sharp knife against the grain.
3. Place the onions at the bottom of a large Dutch oven pot. Mix together with the flour to coat.
4. Wedge the sliced sweet potatoes at the bottom of the pot. Put the meat on top of the sweet potatoes and smear with the mustard.
5. Pour the maple syrup and soy sauce all over the meat and sprinkle generously with black pepper. Pour the wine and water into the pan and cover. Bake for one and a half hours.
6. Place meat together back into the pot and press into the liquid. Add one more cup of liquid (water, wine, or whatever you like) or just enough to cover the meat. Bake for one and a half more hours.