Preheat your oven to 375°F (190°C). Wash and pat dry the zucchini. Carefully slice each zucchini in half lengthwise. Using a spoon, scoop out the pulp and seeds from the center of each half, leaving about a 1/4-inch border. Lightly salt and pepper the inside of the zucchini boats.

Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the diced yellow onion and cook for 3-4 minutes, until softened and translucent. Stir in the minced garlic and cook for another minute until fragrant.

Add the ground chicken breast to the skillet, breaking it up with a spoon. Cook for 5-7 minutes, stirring occasionally, until the chicken is browned through. Drain any excess grease if necessary.

Stir in the marinara sauce, Italian seasoning, 1/2 cup of the shredded mozzarella, salt, and black pepper. Bring the mixture to a gentle simmer and cook for 2-3 minutes, allowing the flavors to meld. Remove from heat.

Arrange the hollowed zucchini halves in your 9x13 inch baking dish. Evenly spoon the chicken filling into each zucchini boat, mounding it slightly.

Pour about 1/4 cup of water into the bottom of the baking dish (this helps steam the zucchini). Cover the baking dish tightly with aluminum foil and bake for 20 minutes, or until the zucchini is just tender.

Remove the foil. Sprinkle the remaining 1/2 cup of shredded mozzarella and the 1/4 cup of grated Parmesan cheese over the stuffed zucchini. Return the dish to the oven, uncovered, and bake for another 10-15 minutes, or until the cheese is melted, bubbly, and lightly golden.

Let the zucchini boats rest for a few minutes before serving. Garnish with fresh chopped parsley and enjoy!