Heat 2 tbsp (30 ml) of the oil in a large frying pan, add the chicken breasts and saute over a medium heat for about 5 minutes until they have changed color on all sides. Remove with a slotted spoon and drain on kitchen paper.
Cut the onions in half, through the root. Trim off the root, then slice the onion halves lengthways to create thin wedges.
Heat the remaining oil in the pan, add the onion wedges and red pesto, and cook gently, stirring constantly, for about 3 minutes until the onion is softened, but not browned.
Add the red wine and water to the pan and bring to the boil, stirring all the time. Then return the sauteed chicken breasts to the pan and add salt and freshly ground black pepper to taste.
Reduce the heat, then cover the pan and simmer gently for about 20 minutes or until the chicken is tender, stirring occasionally to stop it sticking to the bottom of the pan.
Add the grapes to the pan and cook over a low to medium heat until heated through. Check the seasoning, then add more salt and pepper if necessary. Serve the chicken hot, garnished with fresh basil leaves.
Use green pesto instead of red, and substitute a dry white wine for the red, then finish with seedless green grapes. A few spoonfuls of mascarpone cheese can be added at the end, if liked, to enrich the sauce.