Prep the aubergine: Heat your oven to 220°C/425°F. Line two baking sheets with parchment and lightly oil or spray them. Slice the aubergines lengthwise or into 1 cm (1/2-inch) rounds for easier layering.

Season and roast: Lay the slices in a single layer. Brush both sides with olive oil and season with salt, pepper, and oregano. Roast for 20–25 minutes, turning once, until soft and lightly browned. Reduce oven to 190°C/375°F.

Make a quick sauce: While the aubergine roasts, warm 1 tablespoon olive oil in a saucepan. Sauté onion (if using) for 4–5 minutes until translucent. Add garlic and cook 30 seconds. Stir in marinara, a pinch of salt, chili flakes if you like heat, and half the basil. Simmer 10 minutes to thicken slightly.

Prep the topping: In a bowl, combine breadcrumbs with 1/2 cup grated Parmesan. Melt the butter and drizzle it over the crumbs, tossing to coat. Add a pinch of salt and pepper.

Assemble the bake: Spoon a thin layer of sauce into a 23 x 33 cm (9 x 13-inch) baking dish. Add a layer of roasted aubergine. Top with more sauce, a scattering of mozzarella, and a sprinkle of Parmesan. Repeat layers until you’ve used everything, ending with sauce and the remaining mozzarella and Parmesan. Finish with the breadcrumb mixture.

Bake: Cover loosely with foil (tent it so it doesn’t touch the cheese) and bake 20 minutes. Remove foil and bake 15–20 minutes more, until the top is golden and the edges are bubbling.

Rest and finish: Let it rest 10–15 minutes so it sets and slices cleanly. Top with the remaining fresh basil before serving.

Serve: Scoop generous portions. Add a green salad with a zippy vinaigrette, garlic bread, or buttered spaghetti on the side.