Sausage and mushroom pasticciata

Ingredients

• 375 ml pouring cream (1½ cups)
• 200 gm finely grated parmesan
• 375 gm buffalo mozzarella (3 small balls), sliced
• Sausage and mushroom ragù
• 40 gm dried mushrooms, such as porcini
• 2 tbsp olive oil
• 1 onion, finely chopped
• 2 garlic cloves, finely chopped
• 750 gm pork and fennel sausages, skins removed
• 200 ml red wine
• 800 gm canned chopped tomatoes or tomato polpa
• 3 thyme sprigs, plus extra to serve
• 1 tbsp red wine vinegar, or to taste
• Parmesan polenta
• 250 gm coarse polenta
• 50 gm finely grated parmesan
• 50 gm butter, diced