Preheat the oven to 190 degrees Celsius/ 370 degrees Fahrenheit.
Slice the oranges into thin slices, remove the seeds if necessary. Place half of the pieces in a buttered baking dish.
Mix topping: Pick the dill leaves. Chop the dill leaves finely and mix them with soft butter, some salt, and pepper. Blend with an immersion blender, and mix in the grainy mustard.
Bake: Dry the fish with kitchen paper. Spread the dill-butter mixture evenly on top and place the fish in the baking dish. Cover with the remaining orange slices. Pour the broth in the dish and place it in the oven for about 15-17 minutes. It should be slightly undercooked, it will continue cooking a little bit while it stands.
Take out of the oven and pour the broth into a small saucepan. Turn off the oven and place the salmon back in until you make the sauce, leaving the oven door cracked so that the fish doesn’t overcook in the meantime.
Rice: While the fish is in the oven make the orange rice. Heat the olive oil into a saucepan, add the rice and stir it in for about 3 minutes.
Cook rice: Add the chicken stock, half of the zest and the orange juice, and some salt, bring to a boil, lower the heat, and simmer, covered, until all the liquid has been absorbed and the rice is tender about 18–20 minutes or according to the packet's instructions. Fluff with a fork and add the remaining zest and orange juice.
White wine sauce:
Add the heavy cream and the white wine to the saucepan with the vegetable broth and cook on high heat, uncovered, for about 5 minutes.
Thicken: Mix the cornstarch with some cold water until you have a thick yet runny paste. Pour slowly into the cooking sauce. You don't have to add all the corn starch mixture, just enough to thicken the sauce to your liking. Let bubble shortly and adjust the taste with salt and pepper.