Preheat the oven to 205°C (400 °F).
Cook the quartered potatoes in a large pot filled with boiling salted water. Boil until they are nice and soft. Drain the water from the pot using the lid, taking care to leave a little cooking water in the pot.
Add a few tablespoons of butter and 1 cup of broth, and mash well. Add a little more butter and broth in order to obtain a relatively consistent mash.
Add the parsley and chives, then salt and pepper to taste. Mash again and cover. Set aside.
Place the duck thighs skin side up on a rack and reheat them in the oven for 10-12 minutes on the middle rack. Broil them for a few minutes at the end of cooking so that they are nicely browned.
Remove from the oven and serve one leg per serving on a generous bed of parsley mashed potatoes and cover with the orange and raspberry sauce. Garnish with orange quarters and fresh raspberries.
In a small pot, simmer the first four ingredients, slowly whisking.
Add the butter and a few pinches of fleur de sel. Mix until the butter is melted. Remove the pot from the heat and set aside.
For a smoother sauce, you can add a little cornstarch diluted in some water at the end of cooking.
