3. Make the Filling
Heat the oil in a medium skillet over medium-high heat. When the oil is shimmering, add the mushroom stems, garlic, and shallots. Season with the all-purpose seasoning. Cook, stirring frequently, until the stems are soft, about 5 minutes. Transfer to a medium bowl.
Add the cream cheese, ¼ cup of the Parmesan, breadcrumbs, and the 2 tablespoons parsley. Stir until evenly combined.