Marya found this great recipe on the blog Fat Free Vegan, and I just had to try it for St. Patrick's Day.
You'll find the recipes here for both the coddle and the sausages.
First I made the sausages.
Next, I stacked in a Dutch oven: a layer of potatoes, then onions, then the sausage, then more potatoes, topping off with more onions. The stack ends up being high, and only a cup and a half of liquid goes in. The result is, as this Wikipedia entry mentions, it is semi-boiled and semi-steamed.
It was delicious!