1. Rinse the aubergines and remove their stems. Cut them in chunks and leave them in a large bowl filled with water for 10 minutes. Peel the potatoes and cut them into 4. Warm the olive oil in a casserole-type pan and stir fry the garlic for 2 minutes. Squeeze the aubergines with your hands to remove the excess liquid and add them to the garlic along with the potatoes. Give everything a good toss to get them coated in oil.
2. Add the tomato paste, sugar and the finely chopped tomatoes. Add just enough water to cover the food, 1 glass approximately. Season with salt and pepper and add the bay leaf.
3. Simmer the food, over low heat, for about 25 minutes until the vegetables go soft and the sauce reduces. When the sauce thickens it is ready.