Wash ducks and pat dry. Rub with salt and pepper and place on the fat pan of the oven. Peel onions, dice them coarsely and add. Wash the herbs and place them with the bay leaf in the fat pan.
Pour in the wine and stock and roast the ducks in the preheated oven (electric range: 200 °C/ gas: level 3) for about 1 1/4 hours. In the meantime, wash, halve and seed the grapes. Remove ducks from the oven and keep warm.
Pour the stock through a sieve and fill up to 1/4 litre with water. Stir cream and flour until smooth, stir into the boiling sauce and bring to the boil once. Season to taste with salt and pepper.
Melt butter, add grapes and heat briefly while stirring. Arrange the grapes and ducks on a plate and serve with the sauce.