Peel potatoes and cut them into ¼ inch (5mm) slices.
Slice off stalk and bottom ends of eggplant. Cut them lengthwise into ¼ inch (5mm) slices.
Over medium heat, add ¼ cup (100ml) of olive oil to a large frying pan and fry the sliced potato in batches. Make sure to turn them over to cook both sides. The potato slices should be fried until slightly soft, about 4-5 minutes on each side.
In the same frying pan, add ¼ cup (100ml) of olive oil and over a medium heat, start frying the eggplant slices in batches, adding olive oil regularly.
In the same pan, add ¼ cup (100ml) oil and sauté the diced onion until translucent. Add ground meat to the onions in the frying pan and mix well to break up the meat.
Dilute tomato paste in ½ cup (100ml) of water and add to pan.
Once the flour is fully incorporated, gradually add the 4 cups (1l) of milk while stirring continuously. Turn up the heat slightly to bring the thick sauce to a boil and then remove the saucepan from the heat.
Place baking pan into an oven preheated to 350F/80C, and bake for 40 minutes or until the top is nicely browned.