Preheat your oven to 375°F (190°C).

Gently clean the mushrooms under cold water, then pat them dry and remove the stems.

Cook the bacon in a skillet over medium heat until crispy, about 5–7 minutes.

In the same skillet, sauté the diced onion and chopped mushroom stems in reserved drippings until tender.

In a mixing bowl, combine cream cheese, cheddar cheese, crumbled bacon, onion mixture, garlic powder, and black pepper.

Fill each mushroom cap with the cream mixture.

Sprinkle breadcrumbs over the filled caps.

Bake for 20 minutes until mushrooms are tender and tops are golden brown.

Sprinkle chopped parsley over the top before serving.