01 - Preheat your oven to 400°F (200°C). Line a baking dish with parchment paper or lightly grease it.
02 - Slice the zucchini in half lengthwise. Use a spoon to carefully scoop out the center flesh, leaving approximately a 1/4-inch border to form boats. Reserve the scooped-out flesh and finely chop it.
03 - Place the prepared zucchini halves cut side up in the baking dish.
04 - Heat 1 tablespoon of olive oil in a skillet over medium heat. Add the chopped onion and minced garlic, sautéing for 2–3 minutes until softened. Incorporate the chopped zucchini flesh and cook for an additional 3–4 minutes, stirring, until excess moisture has evaporated. Remove from heat and allow to cool slightly.
05 - In a large mixing bowl, combine the shredded mozzarella, 1/2 cup grated Parmesan, ricotta cheese, 1/2 cup fresh breadcrumbs, chopped parsley, dried Italian herbs, salt, and black pepper. Add the cooked onion-zucchini mixture and blend until thoroughly combined.
06 - Spoon the cheese filling evenly into the zucchini boats, applying gentle pressure to pack it in.
07 - In a small bowl, combine the topping Parmesan cheese and 2 tablespoons fresh breadcrumbs. Sprinkle this mixture evenly over the filled zucchini boats. Drizzle with the remaining 1 tablespoon of olive oil.
08 - Bake in the preheated oven for 25–30 minutes, or until the zucchini is tender and the topping is golden brown.
09 - Allow the stuffed zucchini to cool slightly before serving. Garnish with additional fresh parsley, if desired.