Worcestershire sauce. Taste the mixture; it should be savory and a bit tangy. (You can season with a pinch of salt and pepper if you like, but to honor the 4-ingredient spirit, it’s not required.)
Pour over and cover: Pour the stock and Worcestershire mixture evenly over the sausages and onions. The liquid should come at least halfway up the sausages. Cover the slow cooker with the lid.
Slow cook until tender: Cook on LOW for 6–8 hours, or
