Preheat your oven to 400°F and line a baking sheet with parchment paper.
Gently wipe the portobello mushrooms clean with a damp paper towel and remove the stems.
Finely chop the mushroom stems and set them aside to use in the filling.
In a medium skillet, heat the olive oil over medium heat and sauté the minced garlic, chopped mushroom stems, and spinach until the greens are wilted.
Add the ground turkey to the skillet, seasoning with sea salt and black pepper, and cook until the meat is fully browned and crumbled.
Stir the fresh parsley into the turkey mixture and remove the skillet from the heat.
Place the mushroom caps on the prepared baking sheet, gill-side up, and spoon the turkey filling generously into each cap.
Sprinkle the tops with parmesan cheese and roast in the oven for 15 to 20 minutes until the mushrooms are tender.
Drizzle the balsamic glaze over the stuffed mushrooms just before serving.