Vegetarian Stuffed Mushrooms

Preheat the oven to 350 degrees F (175 degrees C).

Brush both sides of each mushroom cap with Italian dressing. Arrange mushrooms on a baking sheet, gill-sides up.

Bake in the preheated oven until tender, about 12 minutes. Drain any juice that has formed in the mushrooms. Leave the oven on.

Heat butter in a pot over medium-high heat. Saute onion and garlic in the hot butter until soft, 5 to 7 minutes. Stir spinach, cream cheese, Parmesan cheese, and 3 tablespoons bread crumbs into the onion mixture until combined.

Divide spinach mixture over mushroom caps; sprinkle with remaining bread crumbs. Return mushrooms to the oven.

Bake in the preheated oven until topping is golden brown and cheese is melted, about 10 minutes.