Heat the oven: Preheat to 400°F (200°C). Lightly oil a large baking dish or line it with parchment for easy cleanup.

Prep the zucchini: Slice each zucchini in half lengthwise. Use a spoon to scoop out the center seeds and flesh, leaving a 1/4-inch border to form boats. Reserve about 1/2 cup of the chopped zucchini flesh and pat it dry.

Season the boats: Brush the cut sides with 1 tablespoon olive oil. Sprinkle with salt and pepper. Arrange them cut-side up in the baking dish.

Sauté aromatics: Warm the remaining 1 tablespoon olive oil in a skillet over medium heat. Add garlic and the reserved chopped zucchini. Cook 2 to 3 minutes until fragrant and slightly softened.

Build the filling: Stir in the cooked chicken, marinara sauce, Italian seasoning, and a pinch of red pepper flakes if using. Simmer 2 to 3 minutes to marry the flavors. Taste and adjust salt and pepper.

Pre-bake the shells (optional but helpful): If your zucchini are very thick, bake the empty shells for 5 to 7 minutes to jump-start tenderizing. This helps avoid undercooked boats.

Fill the boats: Spoon the chicken mixture evenly into each zucchini half. Don’t shy away from a generous mound; it will settle slightly as it bakes.

Add cheese: Top each boat with shredded mozzarella, then sprinkle with Parmesan for that classic Chicken Parm finish.

Bake: Return the pan to the oven and bake 15 to 20 minutes, until the zucchini is tender when pierced with a knife and the cheese is melted and bubbly.

Broil for color: For golden tops, switch to broil for 1 to 2 minutes. Watch closely so the cheese doesn’t burn.

Garnish and serve: Let the boats rest 3 to 5 minutes. Scatter chopped basil or parsley on top. Serve warm with a crisp salad or roasted veggies.