Preheat your oven to 400°F (200°C) and line a small baking sheet with parchment paper.
Carefully clean the portobello mushrooms with a damp paper towel, remove the stems, and use a spoon to gently scrape out the dark gills.
Finely chop the mushroom stems and set them aside.
Heat the olive oil in a non-stick skillet over medium heat; add the minced garlic and chopped mushroom stems, sautéing for 2 minutes until fragrant.
Add the ground turkey to the skillet, breaking it up with a spatula, and cook until browned and no longer pink.
Stir in the fresh spinach, parsley, basil, sea salt, and black pepper, cooking just until the spinach has wilted.
Place the mushroom caps on the prepared baking sheet, gill-side up, and divide the turkey mixture evenly between the two caps.
Top each stuffed mushroom with the grated parmesan cheese.
Bake in the oven for 15 to 20 minutes until the mushrooms are tender and the cheese is slightly golden.
Remove from the oven and finish with a drizzle of balsamic glaze before serving.