For the mustard vinaigrette:
1. In a small bowl, whisk together the mustard, lemon juice and vinegar.
2. Slowly whisk in the olive oil and vegetable broth. Stir in the shallots and chives. Season with salt and pepper.
For the snap peas and new potatoes:
3. Put the potatoes and peas in a large steamer. Set the steamer over simmering water and cook, covered, until the potatoes are tender, about 8 minutes.
4. While the vegetables are still hot, toss them with a few tablespoons of the mustard vinaigrette. Set aside at room temperature while you cook the salmon, or refrigerate for longer storage.
For the salmon:
5. Brush the salmon fillets with some of the mustard vinaigrette and generously season with salt and pepper.
6. Spray a grill grate with non-stick cooking spray and preheat the grill.
7. Place the salmon on the grill and cook for 3 to 4 minutes on each side. Thicker fillets may need to be finished in a 350°F oven for about 5 minutes.
8. To serve, divide the steamed peas, potatoes (these should be served at room temperature) and greens among 4 plates. Place a grilled fillet of salmon on each plate alongside the vegetables. Drizzle a little of the remaining vinaigrette on each plate.