Rinse and dry the fish. Chop together finely the onion and parsley leaves. Shell the peas. Dilute the tomato paste in 1 ladleful hot water.
Sweat the onion and parsley in the oil in a pan over low heat for a few minutes. Add the peas, the diluted tomato paste, and as much boiling water as needed just to cover the peas. Season with salt and pepper and continue cooking over medium heat fo