This is such an easy dish to make and includes one of our favorite fruits - Italian prune plums. Requiring few ingredients and little time, you will love this when plums are in season in late August and September. Serve with polenta and a baguette to sop up the sauce. Pass a simple tossed arugula salad at the table.
Slice plums in half and discard pits. Set aside. Prick sausages 4 or 5 times with a sharp paring knife.
Heat olive oil in a large pan over medium heat and add sausages. Turn frequently and cook until a brown crust has formed on each side (about 10-12 minutes). Remove from the pan and place on a plate. Depending on how fatty the sausage, pour off some (but not all) of the fat.
Reheat pan to medium. Add minced shallot and saute for about 1 minute. Add garlic and sage and stir. Add plums and juices. Season with salt and pepper and add a pinch of sugar if plums are very tart. Stir and saute until the juices begin to sizzle, about 3 minutes.
Pour in wine, increase heat, and simmer for about 5 minutes. Place sausages back into the pan, cover and reduce heat to a gentle simmer. Braise for about 30 minutes, occasionally turning sausages. Make polenta while the sausages cooks.
To finish: transfer sausages to a platter, lift the plums from the pan with a slotted spoon and arrange around the sausages. Return the braising liquid to the stove and reduce liquid by about half. Taste for salt and pepper. Pour over the sausages and plums. Serve with polenta, rice, and/or thick crusty bread.