1. Heat the oil in a large ovenproof frypan over medium-high heat. Add the onion and garlic and stir occasionally until golden (seven to 10 minutes).
2. Add tomato paste and stir continuously for two minutes,then add stock,tomato,wine,cinnamon,fresh oregano and half a teaspoon of dried oregano and bring to a simmer.
3. Add the chopped eggplant and cook over low-medium heat,just below simmering point,for one hour or until the eggplant is completely soft and the sauce has reduced to a slightly runny chutney-style consistency. Remove from heat and remove the cinnamon quill. (If your frypan isn't ovenproof,transfer the cooked eggplant and tomato sauce to a casserole dish.)
4. Preheat the oven to 170C (160C fan-forced).
5. To make the cheese sauce,add the butter to a saucepan over medium heat and swirl until melted. Add the flour and whisk frequently until combined (one to two minutes). Add milk in batches,stirring well after each addition,until all the milk is incorporated,then stir occasionally until thick (three to five minutes). Remove from heat,stir in the two cheeses and egg yolks,the half teaspoon of nutmeg and season to taste.
6. Pour the cheese sauce over the eggplant mixture and spread evenly to create a flat surface.
7. Allow to cool slightly before adding the potato,arranging and overlapping the discs in an even layer. Sprinkle with a pinch each of dried oregano and nutmeg,place in the oven and cook for approximately one hour. For the final 15 minutes,turn on the grill top function to help crisp the top of the potatoes. Keep a close eye on them during this time to ensure the potato doesn't burn.
8. Remove,scatter with extra oregano leaves and serve hot.
If you like this recipe try Katrina'smaple chipotle sweet potato gratin.
Find more of Katrina Meynink's recipes in theGood Food Favourite Recipes cookbook.