Heat ½ tbsp (about 30 ml) of the oil in a frying pan, add the chicken thighs and saute over a medium heat for about 5 minutes until they have changed color on all sides. Transfer the chicken to a flameproof casserole.
Add the onion and celery to the frying pan and cook gently, stirring frequently, for about 3 minutes until softened. Add the garlic, tomatoes, wine and rosemary to the pan. Season well with salt and pepper. Shell half the prawns, then add all the prawns to the tomato sauce and heat until they are cooked.
Pour the tomato sauce over the chicken. Cover and cook gently for 40 minutes or until the chicken is tender when pierced.
About 10 minutes before serving, add the remaining oil and the butter to the frying pan and heat until the mixture is hot but not smoking. Add the triangles of white bread and shallow-fry for about 2 minutes on each side, or until they are crisp and golden. Drain on kitchen paper. Season.
Dip one of the tips of each fried bread triangle in parsley to garnish. Serve the dish piping hot, decorated with the bread triangles.