Peel and finely dice the onion. Chop the herbs. Chop the garlic.
Mix the tomatoes with the tomato paste, the herbs of the cornstarch and pepper and salt well.
Fry the chopped onions in 2 tablespoons of oil. Add the peas and garlic and cook for about 2 minutes. Add the tomato and herb mixture and let it simmer for 3 minutes.
Fry the prawns in the remaining olive oil for 2-3 minutes on each side.