Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper. Slice zucchini in half lengthwise and scoop out the flesh to create boats.

In a skillet, heat olive oil over medium heat. Add minced garlic and chopped onion, sauté for about 2 minutes until fragrant and translucent.

Stir in chopped mushrooms and cook for 3-4 minutes until softened. Add fresh spinach and cook until wilted, about 2 minutes.

In a large bowl, mix ricotta and Parmesan with sautéed vegetables. Season generously with salt, pepper, and optional red pepper flakes.

Fill each zucchini boat with the ricotta mixture, heaping generously. Arrange on the prepared baking sheet.

Bake for 20-25 minutes until zucchini is tender and filling is golden.

Remove from oven, garnish with fresh basil, and serve warm.