Preheat the oven to 200°C (180°C fan-forced).
Line 2 baking trays with paper for the sliced eggplant, and line a third tray or small dish for the whole eggplant.
Pierce the whole eggplant a few times with a skewer, put it in the dish/tray, together with the whole head of garlic and then tranfer it into the oven.
Slice one eggplant thinly, with the slices as even as possible, and arrange on the tray.
Mix 1/4 cup olive oil in a dish with 1/2 tsp of your favourite salt (I like to use smoked salt for this dish), and brush each eggplant slice, top and bottom with the mixture, and put into the oven.
Cook the eggplant slices for about 20 minutes until they turn golden. Remove from the oven, and and set aside to cool.
Cook the whole eggplant for about 45 minutes, until it is soft and malleable when pressed with your fingers. Remove from the oven and set aside to cool.
Put the eggplant slices in a jar and pour olive oil over the top to immerse them, then store in the fridge.