Heat the olive oil in a large ovenproof frying pan or shallow casserole over medium heat. Add the onion and garlic and cook until softened and fragrant.
Add the lamb and beef mince, breaking it up with a spoon, and cook until browned. Stir through the Gewürzhaus Lamb Spice until evenly coated.
Pour in the red wine, tomato passata and water, then add the bay leaves and season with salt and pepper. Bring to a simmer and cook for 15 minutes.
Add the potato, zucchini and eggplant, stirring to combine. Continue to simmer for around 40 minutes, stirring occasionally, until the sauce has thickened and the vegetables are tender. Remove from the heat.
In a separate saucepan over medium heat, melt the butter for the béchamel. Add the plain flour and cornflour and cook briefly, stirring, until combined.
Gradually whisk in the milk, adding a little at a time and whisking continuously to avoid lumps. Continue until the sauce is smooth and thickened.
Stir in the grated cheese, then season with nutmeg and salt.
Spoon the béchamel evenly over the meat and vegetable mixture and smooth the surface. Sprinkle with extra cheese.
Bake in a 180°C fan-forced oven for 25–30 minutes, or until the top is golden.
Allow to rest for 20 minutes before serving to help it set. Serve warm.
