Chop the peppers into one-inch squares, removing every seed. Simmer in oil for 30 minutes. Slice the onion across and quarter it. Cut the cleaned leeks into half-inch pieces. Cut the aubergine into cubes and sprinkle these with salt. Set them to drain.
Start cooking the onions and leeks in a pan with 1½ pints cold water. Cube the potatoes and add them after 15 minutes with ½ pint stock.