Cut the zucchinis in half lengthwise and scoop out the seeds and flesh to create boats, leaving about 1/4 inch of the flesh on the skin. Set aside the scooped zucchini flesh for later use.
In a skillet over medium heat, add the ground chicken and cook until browned, breaking it apart with a spatula (about 5-7 minutes).
Add the minced garlic and the reserved zucchini flesh to the skillet, sautéing for an additional 2-3 minutes until soft and fragrant.
Stir in the marinara sauce, Italian seasoning, salt, and pepper. Let it simmer for a few minutes to meld the flavors.
Remove the skillet from heat and mix in half of the mozzarella cheese and all of the Parmesan cheese until well combined.
Stuff each zucchini boat with the chicken and sauce mixture, packing it in generously.
Sprinkle the remaining mozzarella cheese and breadcrumbs evenly over the top of each stuffed zucchini.
Place the zucchini boats in a baking dish and cover with foil. Bake in the preheated oven for 25 minutes.
Remove the foil and bake for another 10-15 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let cool slightly before garnishing with fresh basil.
Notes
Panko breadcrumbs give a nice crunch to the topping.