Peel and crush the garlic, sprinkle with olive oil and salt and let it infuse until needed.
Preheat the oven to 200ºC.
Cut the marrow evenly into 6 chunks/slices. Cut the two ends off so that they can all stand in a casserole dish. Scoop the middle out of the marrow but leave a little in the bottom to form a base. Drizzle the marrow slices with some oil and roast in a casserole dish for 30 minutes.
In the meantime, prepare the filling. Slice the aubergine, drizzle with oil and grill on each side for 10min. Peel and dice the onion and soften them in a skillet on medium heat for 5 min with some oil. Cut the tomatoes into small chunks and add them to the skillet. Cut half of the cut-out marrow into small chunks and add them also to the skillet. Mix well and cook on medium heat. Now add the other ingredients; garlic, oregano, vinegar, cut basil leaves, soft cheese and some salt and pepper. Mix and reduce the heat to low.
Once the aubergines are ready, cut them into small chunks and stir them under the tomato mixture. Spoon the filling into each marrow slice, scatter over parmesan cheese and return to the oven for 10min.
Sprinkle with additional parmesan cheese on top and serve.