Remove the casing from the sausage and crumble the meat.
Wash the rosemary, strip the leaves from the stem, and finely chop them with a mezzaluna or chef's knife on a cutting board.
Peel and finely mince the shallot.
Add the olive oil and minced shallot to a skillet and place it over heat.
Gently sauté the shallot until golden, then increase the heat and add the crumbled sausage, a teaspoon of the chopped rosemary, and a grind of black pepper. Brown evenly over medium heat.
Pour in the white wine and allow it to evaporate uncovered. Tilt the skillet to one side and spoon out any excess fat.
Stir in the tomato passata, bring back to a simmer, then cover and cook over low heat for 20 minutes.
Once the sauce is ready and nicely thickened, proceed with preparing the polenta.