Cut the chicken breasts into strips. Also cut the Parma ham into strips.
Sear the meat with the onions, preferably in olive oil. When the meat is lightly browned, add the Parma ham and sage and sauté briefly. Deglaze with the white wine. Bring to the boil and simmer for 3-5 minutes, then add the beef stock and the cream. Bring to the boil and simmer for 20 to 30 minutes with the lid on.
If the sauce is too runny, mix the starch with a little water, add and cook for 2-3 minutes. Season to taste and, if necessary, add salt, but the stock and Parma ham should have enough salt.