Preheat the oven to 450°F.
In a big bowl, toss the potatoes with 2 tablespoons of the olive oil, ½ teaspoon sea salt and ½ teaspoon pepper. Unfold them out on a 9-by-13-inch sheet pan, reserving the bowl, and roast within the oven for quarter-hour.
In the meantime, in the identical bowl, toss the string beans with 1 tablespoon of the olive oil, ½ teaspoon sea salt and ½ teaspoon pepper and put aside.
Make the Dijon-walnut combination. In a small bowl, combine collectively the walnuts, Dijon, remaining 1 tablespoon olive oil, lemon juice, parsley and ¼ teaspoon sea salt. Unfold the combination over the flesh facet of the salmon fillets.
When the potatoes have cooked for quarter-hour, add the salmon to the sheet pan, pushing the potatoes apart, as wanted. Add the string beans, becoming them in throughout the pan. Roast for about quarter-hour extra or till every part is cooked to your liking.
