Start out peeling the potatoes, then splitting them in half. Split each half lengthwise into quarters and place in the bottom of a large crock pot. Peel and slice the onion, then place it into the crock pot and mix them up with the potatoes.
Place the roast on top of the potatoes and onions. Pour the broth over the roast, then sprinkle the spices over the top of the roast and a little around the sides onto the potatoes (especially the cinnamon and pepper). I would also recommend using a lesser amount of cardamom to start (you can always add a dash more near the end), as it can be a bit overpowering. Put the lid on the crock pot and set it to low for eight hours (ours has automatic timer settings for low and high).
After the eight hours has passed, you should have a well-braised roast on a bed of soft sweet potatoes and tender onions, all steeped in broth and spices not often associated with beef roasts. Transfer the roast to a cutting board and cut clear of the bone. Transfer the potatoes and onions to a serving bowl. Reserve the juices in a small bowl or glass measuring cup.
To serve, slice the roast across into thin slices and place several on a plate. Arrange the sweet potatoes along side, either with the onions mixed in, or separate the onions and place over the roast. Spoon a tablespoon or two of the reserved juices over the meat. And in the interest of not wasting a lot of time preparing sides, we finished it off with a simple salad of mixed greens and balsamic vinegar.
If you like gravy (we’re personally not fans), you can skim the excess fat from the top of the reserved juice instead, then transfer 1-1/2 cups of the juice to a small sauce pan. Dissolve 1-1/2 tbsp arrowroot powder in 3 tbsp cold water, then whisk into the juices while heating over medium heat. Continue whisking and cooking until it comes to a low boil, then about two to four minutes longer until it thickens. Remove from the heat and serve over the meat instead of the juice above.