Making stuffed Portobello mushrooms is straightforward if you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 375°F (190°C).
2. Prepare the Mushrooms: Clean the Portobello mushrooms with a damp cloth. Remove the stems and gills using a spoon for a smooth surface.
3. Make the Filling: In a mixing bowl, combine the cooked quinoa, chopped spinach, ricotta cheese, shredded mozzarella, minced garlic, Italian seasoning, red pepper flakes (if using), salt, and pepper.
4. Fill the Mushrooms: Drizzle the insides of each mushroom with olive oil. Then, generously fill each mushroom cap with the prepared filling.
5. Arrange on a Baking Sheet: Place the filled mushrooms on a baking sheet, ensuring they are upright to prevent filling from spilling out.
6. Bake: Bake in the preheated oven for 25-30 minutes, or until the mushrooms are tender and the filling is golden and bubbly.
7. Garnish: Once cooked, remove the mushrooms from the oven, garnish with chopped fresh parsley, and let cool for a few minutes before serving.

These steps will guide you in creating stuffed Portobello mushrooms effortlessly.