Saute chicken and onion in olive oil until slightly brown. Extinguish with wine, add 2 cups water, cover and simmer for about 35 minutes. Add the potatoes, a little more water, if required, and continue boiling for 15 minutes with the lid on. Add courgettes, purslane, tomatoes, salt, pepper and toss the pot in order to mix well all vegetables with the chicken. Simmer for 25-30 minutes, until only the oil remains. Serve somewhat warm or even cold.