Preheat your oven to 400°F (200°C). Halve the zucchinis lengthwise and scoop out the seeds. Brush cut sides with olive oil and roast for 15 minutes.

In a skillet, add olive oil and sauté minced garlic until fragrant, about 1-2 minutes. Add chopped mushrooms and cook for 5 minutes until softened. Stir in spinach until wilted, then remove from heat and let cool before adding cheese and seasonings.

Stuff the roasted zucchini with the filling, packing it in generously. Optionally, sprinkle breadcrumbs and extra mozzarella on top.

Return the stuffed zucchinis to the oven and bake for 15-20 minutes until the cheese is gooey and bubbling. Check for a golden top before serving.