Heat a large nonstick skillet over
medium-high heat. Add sausages and
brown on all sides, about 10 minutes.
Meanwhile, coat the bowl of a slow
cooker with nonstick cooking spray.
Place butter, brown sugar and mustard
in slow cooker; stir in onions, caraway
seeds, salt and pepper. Place sausages
over onions and pour beer over the top.
Cover and cook on HIGH for 4 hours.
Serve sausages on rolls with onions. Top
with mustard and cheddar, if desired.