Ingredients

• cooking spray

• 1 tablespoon salted butter

• 1/4 cup Italian-seasoned breadcrumbs

• 8 ounces hot Italian pork sausage

• 2 (8-ounce) packages sliced fresh cremini mushrooms, chopped (about 5 cups)

• 1 tablespoon finely chopped garlic (from 3 medium garlic cloves)

• 1/2 teaspoon freshly ground black pepper

• 1/2 teaspoon kosher salt

• 1 cup sour cream

• 1 (7-ounces) container chive-and-onion cream cheese, at room temperature

• 1/4 cup chopped fresh flat-leaf parsley, plus more for garnish

• 3 ounces low-moisture part-skim mozzarella cheese, shredded (about 3/4 cup), divided

• 1/2 cup freshly grated Parmesan cheese, divided

• crostini for serving