Parmesan Quinoa Stuffed Portobello Mushrooms Recipe

Name: Parmesan Quinoa-Stuffed Portobello Mushrooms Recipe
Ingredients: For the Mushrooms:; 6 large portobello mushrooms (cleaned, stemmed, and wiped dry); 2 tablespoons extra-virgin olive oil; 1 tablespoon balsamic vinegar; For the Quinoa Filling:; 1 cup quinoa (rinsed); 2 cups water; 1 tablespoon extra-virgin olive oil; 1 large clove garlic (peeled, smashed, and finely chopped); 1/4 cup grated Parmesan cheese (or Pecorino Romano cheese); 1/3 cup shredded mozzarella cheese; 2 ounces baby spinach (rinsed); 1/4 cup pecans (chopped); Freshly ground black pepper (to taste); 1 1/2 cups marinara sauce (jarred or homemade); Optional: additional parmesan for serving