Heat the olive oil in a large saucepan. Add the onion and cook over moderate heat until softened but not browned, about 5 minutes. Add the garlic and cook until fragrant, about 1 minute. Wrap the coriander seeds and bay leaves in cheesecloth and tie with string. Stir the herb bundle into the saucepan along with the wine, stock, sugar and cayenne and bring to a boil. Reduce the heat, cover and simmer gently for 10 minutes.