Preheat your oven to 180°C (360°F). While the oven heats, lay out your filo sheets and lightly spray each one with olive oil on both sides, layering them into a 9x13 inch baking dish or similar size. Let the sheets drape slightly over the edges—this creates a beautiful rustic crust. Press them gently into the corners so they hold their shape during baking.

Heat a large skillet over medium-high heat and add the diced sweet potatoes. Cook for about 10 minutes until they begin to soften, then add the trimmed asparagus and cook for just 1 minute more. Transfer to a colander, rinse the asparagus under cold water to stop the cooking and preserve its vibrant green color, then set aside to drain. In the same skillet, add a touch of olive oil and sauté the chopped onion for 5 minutes until softened, then add the minced garlic and grated zucchini and cook for 2–3 minutes until the zucchini is tender and any excess moisture has mostly evaporated. I like to squeeze the zucchini really well before cooking—this prevents your quiche from becoming watery.

In a large bowl, whisk together the eggs, low-fat buttermilk, most of the parmesan cheese, crushed red pepper flakes, and a pinch of ground nutmeg. Whisk until completely smooth and well combined. This custard is what will hold everything together and create the creamy, set texture of your quiche.

Spread the cooked potato and zucchini mixture from Step 2 evenly across the filo crust. Arrange the roasted red peppers and drained asparagus on top, distributing them evenly so each slice gets a variety of vegetables. Pour the egg custard from Step 3 over the filling, making sure it flows into all the gaps. Sprinkle the remaining parmesan cheese over the top.

Place the quiche in the preheated oven and bake for 40–45 minutes until the top is golden brown and the center is just set—it should have a slight jiggle in the very middle but shouldn't be liquid. I find the quiche is done when the egg mixture is no longer wet on top and a knife inserted near the center comes out clean. Let it rest for 5 minutes before cutting.

Cut the quiche into portions and garnish each piece with fresh chopped basil. The basil adds a bright, herbaceous finish that complements the roasted vegetables beautifully.