Preheat your oven to 375°F (190°C). Clean the mushrooms and remove their stems. Set aside.
In a large skillet, heat the extra virgin olive oil over medium heat. Add minced garlic and sauté until aromatic but not browned. Add the fresh spinach and cook until wilted.
Season with salt, black pepper, granulated garlic, dried oregano, and fresh basil. Remove from heat and let it cool.
In a mixing bowl, combine the cooled spinach mixture, softened butter, and grated Fontina cheese. Mix until well combined.
Carefully stuff each mushroom cap with the spinach and cheese mixture. Ensure each mushroom is generously filled.
In another bowl, mix the Japanese-style breadcrumbs with chopped fresh parsley. Top each stuffed mushroom with a generous layer of this breadcrumb mixture.
Arrange the stuffed mushrooms on a baking tray. Lightly sprinkle the top with paprika for added color and a slight kick.
Bake in the preheated oven for 15-20 minutes or until the tops are golden brown and the mushrooms are cooked through.
Serve the mushrooms hot, preferably with a side of marinara sauce or your choice of dipping sauce.