Serve the purée with slices of fried sausage on top.
Remarks
This recipe was devised with Morteau sausage in mind, but other types of smoked sausage will work fine.
Natives of the Franche-Comté region, in France, might raise their eyebrows at stage 2: just for once, we'll prick the sausage (which they wouldn't normally do), so that the smoky flavour can spread into the potatoes during cooking.
No need to let all that smoky flavour go to waste: you can use the cooking water left for boiling pasta or rice, for example.