How to Make It
Preheat oven to 425°F. Place potatoes and 1 cup water in a microwavable bowl; cover. Microwave at high 6 minutes. Transfer to a plate; let cool 5 minutes.
Spray a rimmed baking sheet with cooking spray. Place fillets on one side of baking sheet; coat with cooking spray. Place potatoes in middle of baking sheet. Using the flat side of a measuring cup, gently crush potatoes. Drizzle potatoes with oil. Stir together salt and pepper in a small bowl; sprinkle two-thirds of mixture over salmon and potatoes. Bake at 425°F 5 minutes; remove from oven.
Add haricots verts to baking sheet; season with remaining salt mixture. Bake at 425°F 10 minutes. Turn on broiler to high; broil until salmon is browned, about 2 minutes.
Stir together mayonnaise, parsley, shallot, lemon juice, and mustard in a small bowl. Serve salmon, potatoes, and haricots verts with sauce and lemon wedges.