Preheat the oven to 350 degrees Fahrenheit (180 Celsius).
Toss the garlic cloves, zucchini, onion, and mushroom in a large bowl with the olive oil. Season with salt and paper and place on a baking sheet, lined with parchment paper. Roast for 10 to 15 minutes, or until the vegetables are tender.
Remove the cloves of garlic and press gently to remove the cooked garlic from their skins. Add the garlic to the tomato passata and stir through.
Pour the passata over the roasted vegetables and add the chickpeas. Toss to combine and return to the oven to bubble away for another 10 minutes.
Carefully cut the tops off the bell peppers, and scoop out the seeds and membrane. Fill with the veggie mixture and torn basil leaves, and return to the oven and bake for 15 minutes, or until the skin on the bell peppers start to shrivel.
Meanwhile, heat 2 cups of water to a boil. Add the couscous, season with salt and pepper, and stir. Remove from heat and cover for 10 minutes. Fluff with a fork, and serve alongside the vegan stuffed peppers. Top with fresh basil leaves.
Any remaining veggies can be saved and eaten on their own - they're even better the next day!