How to Make It
Add 3 inches of water and 2 teaspoons of salt to a large skillet and bring to a boil. Add the asparagus and cook until barely tender, about 4 minutes. Line a large plate with paper towels and, using a slotted spoon, transfer the asparagus to the plate and refrigerate. Keep the water boiling.
Add the wine to the water in the skillet and return to a boil. Add the salmon and simmer over low heat until just cooked through, about 7 minutes. Transfer the salmon to a plate and refrigerate.
Meanwhile, in a small bowl, mix the vinegar with the mustard. Whisk in the olive oil and season with salt and pepper. In a large bowl, squeeze the juice from the lemon half over the endives and toss well.
Arrange the asparagus on plates or a large platter. Add 1 tablespoon of the dressing to the endives and toss well. Spoon the endives over the bottom of the asparagus. Set the salmon next to the asparagus and drizzle the remaining dressing around the plate. Garnish with the chives and serve.