Preheat oven to 400 degrees.
Clean the mushrooms with a clean damp cloth.
Line a baking sheet with parchment paper.
Place mushroom caps, stem side down, on the prepared baking sheet.
Cooking for 6 minutes.
Remove from oven and transfer to paper towels to drain. Turn the oven to broil.
Meanwhile, heat the avocado oil in a skillet.
Add onion and saute for 6 minutes. Add sun-dried tomatoes and cook for two more minutes. Add garlic and season to taste with salt and pepper. Cook for 30 seconds.
Remove from heat and transfer to a food processor. Add cream cheese and pulse until well combined. (If you don’t have a food processor you can mix by hand.)
Spoon the mixture into the mushroom caps and place on the parchment lined baking sheet. Top with parmesan cheese.
Broil for 3 to 5 minutes, until the cheese is melted and lightly browned.
Top with parsley and serve warm.