In a saucepan, heat the olive oil and sauté the onion and garlic until translucent.
Add the mince and cook until browned.
Deglaze with the wine and add the tomatoes. Cook for 20 minutes until the sauce thickens.
Prepare the béchamel sauce: melt the butter, add the flour, and stir for 1 minute. Gradually add the milk and cook until thickened. Season with salt, pepper, and nutmeg.
Assemble the moussaka in layers: potatoes, mince, eggplants, and top with the béchamel sauce. Sprinkle with Parmesan cheese.
Bake at 180°C (350°F) for 45-50 minutes until the top is golden brown.