Preheat oven to 400°. Grease a baking sheet with cooking spray. Remove stems from mushrooms and roughly chop stems. Place mushroom caps on baking sheet.
In a medium skillet over medium heat, melt butter. Add chopped mushrooms stems and cook until most of the moisture is out, 5 minutes. Add garlic and cook until fragrant, 1 minute then add breadcrumbs and let toast slightly, 3 minutes. Season with salt and pepper. Remove from heat and let cool slightly.
In a large bowl mix together mushroom stem mixture, Parmesan, cream cheese, parsley, and thyme. Season with salt and pepper. Fill mushroom caps with filling and sprinkle with more Parmesan.
Bake until mushrooms are soft and the tops are golden, 20 minutes.
Garnish with parsley to serve.
***Since I used the bigger Portobello mushrooms, I doubled my ingredients on the video. I also did an extra step and cooked the mushrooms for 5 mins without the stuffing, however that is not necessary.
*** Be careful not to add too much salt! Since parmesan cheese has a lot of salt the dish can become salty really fast.