Fill a large pot with an inch or two of water, and insert a steamer basket. Steam the chopped sweet potatoes until just tender, about 10 minutes.
In a large skillet, cook the bacon pieces over medium heat, stirring regularly until browned.
Remove the bacon from the skillet and set aside. (Leave the bacon grease in the pan.) Add the ground beef to the skillet and cook it until it’s brown and cooked through. Add the ground fennel seed, thyme, sage, and salt. Stir to coat evenly, then remove the beef from the skillet.
Add the diced onion to the skillet. Cook over medium heat for a few minutes, until translucent, then add the cooked sweet potatoes to the skillet. Turn up the heat to medium high and cook for a couple minutes to brown the sweet potatoes a bit, stirring regularly. Add the cooked bacon, ground beef, and diced prunes to the skillet. Cook everything together over medium heat for a couple more minutes. Add salt and pepper to taste.