Preheat the oven: Preheat the oven to 400°F and line a baking sheet with parchment paper or lightly grease it with olive oil.
Clean the mushrooms: Wipe mushroom caps clean with a damp paper towel and twist out the stems. Chop the stems finely and set aside for the filling.
Pre-bake the caps: Arrange the mushroom caps hollow-side up on the baking sheet and bake for 5 minutes to release excess moisture. Remove from the oven and let cool slightly.
Cook the turkey bacon: In a skillet over medium heat, cook the turkey bacon until the edges turn crisp and golden, about 6 minutes. Crumble it once cool enough to handle.
Sauté the chopped stems: In the same skillet, add olive oil and the chopped mushroom stems with garlic. Cook for 2 to 3 minutes until softened and fragrant.
Mix the filling: In a bowl, combine softened cream cheese, crumbled turkey bacon, sautéed stems and garlic, half the parmesan, parsley, green onion, salt and pepper. Stir until evenly combined and creamy.
Stuff the mushroom caps: Spoon the filling into each mushroom cap, mounding it slightly above the rim. Arrange the stuffed caps back on the baking sheet.
Top with breadcrumbs: Sprinkle the remaining parmesan and panko breadcrumbs evenly over the filled mushroom caps for a golden, crunchy top.
Bake until golden: Bake at 400°F for 15 to 18 minutes, until the tops turn golden brown and the mushrooms feel tender when pierced with a fork.
Cool slightly and serve: Let the stuffed mushroom bites rest for 2 to 3 minutes before transferring to a platter, since the filling stays very hot.