Cover the porcini with 500ml of boiling water. Peel and finely slice the onions and garlic. Drizzle 2 tablespoons of oil into a large casserole pan over a medium-low heat, add the cinnamon and fry for 1 minute, then add the onion and garlic. Pick in the oregano leaves, pour in the vinegar, then simmer with the lid on for 20 minutes, or until soft and lightly golden, stirring regularly. Meanwhile, slice the aubergines lengthways 1cm thick, then chargrill in batches on a griddle pan.
Scrub the potatoes and slice 1cm thick, then add to the casserole pan with just the porcini water, reserving the mushrooms. Scrunch the tomatoes into the pan, then pour in 1 tin’s worth of water and leave to tick away on a medium heat for 30 minutes, stirring regularly. Preheat the oven to 200ºC/400ºF/gas 6.
Place the mushrooms in a blender with half the feta and the eggs. Pour in the milk, finely grate in half the nutmeg, then whiz until smooth. Season the tomato sauce to perfection with sea salt and black pepper, then spoon half into a 25cm x 35cm baking dish. Cover with half the aubergines, drizzle over 4 tablespoons of creamy sauce, then repeat, finishing with the remaining creamy sauce. Crumble over the rest of the feta, then bake for 40 minutes, or until golden and bubbling.
Delicious served with a simple lemony dressed green salad.