Heat the oven to 325 F (165 C). Brown the sausages lightly in a skillet for 6 minutes, then cut each into two or three pieces.
Cook the bacon in the same skillet for 4 minutes until some fat renders; do not crisp it fully.
Layer and Cook:
Layer half the onion and potatoes in a Dutch oven. Add the sausage and bacon, then the remaining onion and potatoes.
Pour in the stock and water. Add parsley, pepper, and salt. Bring just to a simmer, cover, and bake for 75 to 90 minutes until the potatoes are tender.
Serve:
Taste the broth and adjust salt and pepper. Rest covered for 10 minutes.
Ladle into deep bowls and serve with brown soda bread.
Notes
Traditional coddle is pale rather than deeply browned; color the sausages only lightly.
Use waxy potatoes so the chunks remain intact in the broth.