Place all ingredients except for the sausage into your crock pot (put the peas on the bottom). The peas will grow some during cooking, so do not make more than 3/4 full to start with (ask me how I know). If you do not have bouquet garni, use your favorite blend of herbs for soup. Make sure the liquid at least covers the peas. 3 cups works in my oval pot, but it make take more in yours.
Cook on LO for 4 to 6 hours, depending on crock pot. With my old crock pot, I could cook this for 8 hours on low, but with the new one it's closer to 6. This will also work on High for 2-3 hours.
Place the sausage in for the last 20 minutes of cooking. Ideally, we grill the sausage and stir it in at the table, but in the real world, I've even microwaved the sausage and then stirred it in at the table.
If you are serving a mixed crowd (some vegetarian, some not) make this with the vegetable stock and serve the sausage on the side. It will please both groups, and the soup will not suffer. If you leave out the sausage, you may find that you need to add a second teaspoon of herbs towards the end of cooking. If you have smoked paprika, it is a nice addition to add the smoky flavor that is missing from the sausage.
Taste and adjust seasonings. It sometimes needs salt and pepper. Remove the bay leaf.
Leftovers reheat well and will freeze. If you have a large crock pot, it is an easy recipe to double.