Peel, then cut sweet potatoes into 1-inch cubes. Combine sweet potatoes, 1 tsp salt and enough water to cover by approx. 1-2 inches in a large pot (use same for 4 ppl). Cover and bring to a boil over high heat. Once boiling, reduce heat to medium. Simmer uncovered until fork-tender, 10-12 min. Drain and return sweet potatoes to the same pot, off heat.
Meanwhile, trim ends off broccolini, then cut any larger stalks in half lengthwise, leaving thinner stalks whole. Thinly slice chives. Whisk together Dijon and half the maple syrup (use all for 4 ppl) in a small bowl. Set aside. Open one side of the package of pecans. Using a rolling pin or heavy-bottomed pot, crush pecans in package until broken into small crumbs (or chop finely if preferred).
Pat salmon dry with paper towels. Season with salt and pepper. Coat tops of salmon with maple-Dijon mixture. Sprinkle crushed pecans over top and press down lightly to adhere. Transfer pecan-crusted salmon to a parchment-lined baking sheet. Roast in the middle of the oven until salmon is cooked through, 16-20 min.**
Meanwhile, heat a large non-stick pan over medium heat. When hot, add 1 tbsp (2 tbsp) butter, then broccolini, cranberries and ¼ cup (½ cup) water. Cook, stirring occasionally, until tender, 5-7 min. Add half the chives. Season with salt and pepper, then toss to combine. Remove from heat.
Mash 2 tbsp (4 tbsp) butter and 3 tbsp (6 tbsp) milk into potatoes until smooth. Season with salt and pepper, then stir in remaining chives. Divide pecan-crusted roasted salmon, creamy mash and broccolini between plates.
If you've opted for jumbo salmon, season it in the same way the recipe instructs you to season the regular portion of salmon. To cook jumbo salmon, increase roast time to 16-20 min.