Set the oven at 200˚C/Gas 6.Melt the butter in the oil in a large, deep casserole. Cut the guinea fowl in half through the backbone, salt and pepper it, then colour it lightly on both sides in the butter and oil. Remove and set aside.
Peel the onions and cut them in half and then into thick segments. Put them in the pan in which you browned the guinea fowl halves and leave to colour over a moderate heat.Scrub and roughly chop the carrots, trim and roughly chop the celery, then add them to the onions.
Peel the garlic, crush and add it. Toast the peppercorns in a dry frying pan then crush or grind fairly finely and add them together with the flour.Continue cooking for 3 or 4 minutes then pour in the stock.
Bring to the boil then turn down to a simmer. Season with salt, pepper, the orange peel, bay and the star anise, then return the guinea fowl to the pan.Cover with a lid, then put in the oven and leave to bake for 50 minutes.