Sprinkle the brown sugar evenly over the top of the sausage and apples. Try to cover as much of the surface as you can; this sugar will melt down into a dark, sticky caramel-like syrup.
Cover the slow cooker with the lid and cook on LOW for 4 to 5 hours, or on HIGH for 2 to 2 1/2 hours, until the apples are very tender and the sausage is heated through and glazed. The apples should look soft and the liquid should be thick and syrupy.
Once cooked, gently toss the sausage and apples together in the slow cooker so everything is coated in the dark caramelized syrup, being careful not to mash the apples too much.
Taste and, if you like, sprinkle with a small pinch of salt to balance the sweetness (optional, not counted as an ingredient). Serve warm straight from the slow cooker, making sure each serving gets plenty of sausage, apples, and syrup.
