01 - Preheat oven to 400°F. Line a baking dish with parchment paper or lightly grease it.
02 - Cut each zucchini in half lengthwise. Using a spoon, carefully scoop out the centers, leaving a 1/4-inch border to form sturdy boats. Reserve the scooped flesh and chop it finely.
03 - Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the onion and garlic, sautéing for 2 to 3 minutes until fragrant and translucent.
04 - Add the chopped mushrooms and reserved zucchini flesh to the skillet. Cook for 4 to 5 minutes, stirring occasionally, until the vegetables are softened and moisture has evaporated.
05 - Push the vegetables to one side of the skillet. Add the remaining 1 tablespoon of olive oil, then add the ground turkey. Cook, breaking the meat apart with a spatula, for 5 to 7 minutes until browned and cooked through.
06 - Stir in the salt, black pepper, dried oregano, and red pepper flakes if using. Mix everything together thoroughly.
07 - Remove the skillet from heat. Fold in the basil pesto and chopped fresh basil, stirring until the filling is evenly coated.
08 - Arrange the zucchini boats in the prepared baking dish. Spoon the turkey and mushroom filling evenly into each boat, pressing gently to pack the filling.
09 - Sprinkle the shredded mozzarella and grated Parmesan cheese evenly over the top of each stuffed zucchini boat.
10 - Bake in the preheated oven for 20 to 25 minutes, or until the zucchini is tender and the cheese is golden and bubbly.
11 - Let rest for a few minutes, then garnish with additional fresh basil leaves if desired. Serve warm.