Heat olive oil in a saucepan over medium heat.

Add sliced mushrooms, chopped onion, carrot, celery, and minced garlic to the saucepan.

Cook the vegetables for 5 minutes, or until softened.

Add crushed tomatoes, chopped parsley, chopped basil, dried thyme, and dried rosemary to the saucepan.

Bring the sauce to a simmer and allow it to simmer for 15 minutes.

Season the tomato sauce with salt and pepper to taste.

In a large soup pot, heat water with 1 teaspoon of salt to boiling.

Slowly pour in the cornmeal in a steady stream while continuously whisking.

Reduce the heat to low and simmer, stirring often with a wooden utensil, for 20 minutes.

Continue simmering until the polenta thickens and pulls away from the sides of the pan.

Add butter and grated Parmesan cheese to the polenta.

Stir until the butter and cheese are fully incorporated and the polenta is creamy.

Ladle the polenta into individual serving bowls.

Top each bowl of polenta with the prepared tomato sauce.

Sprinkle extra Parmesan cheese over the polenta and tomato sauce before serving.