Pour 2 tablespoons of the olive oil into the big skillet, and set over medium-high heat. Lay in all the sausages; cook them for 5 minutes or more, rolling them over occasionally, until they’re nicely browned on all sides. Pour in the wine, and boil until it is reduced by half. Remove the sausages to a platter, and pour over them the wine remaining in the pan.

Add the remaining 2 tablespoons olive oil to the empty skillet, toss in the garlic cloves, and cook for a minute or so, over medium heat, until they’re sizzling. Drop the peperoncino in a hot spot for a few seconds, then scatter the squashed olives in the pan; toss and cook for a couple of minutes.

Add the fennel chunks, and stir them in with the garlic and olives. Season the vegetables with ½ teaspoon salt, cover the skillet, and cook over medium-high heat for 20 minutes, tossing and stirring now and then, until the fennel softens, shrinks, and begins to color. Add a bit of water to the pan if the fennel remains hard and resistant to the bite.

When the fennel is cooked through, return the sausages and the wine to the skillet. Turn and tumble the meat and vegetables together, and cook uncovered another 5 minutes or so, until everything is deeply caramelized and glazed. Adjust the seasoning to taste; keep cooking and tumbling the sausages and fennel. Serve piping hot.