Halve the garlic. Heat the oil in a pan and fry the chicken breasts until golden brown. Season with salt and pepper. Add the garlic, deglaze with the chicken stock. Add the rosemary. Cover and cook over medium heat for approx. 40 minutes.
Take the chicken breasts out of the stock. Shake the flour with water in a shaker until smooth, stir into the stock and bring to the boil. Possibly season with salt and pepper.