1 Extra-virgin olive oil (divided)
1 tbsp Dijon mustard
3/8 tsp Salt
3/8 tsp Pepper
4-5 (6 oz) Boneless, skinless salmon fillets (about 1 inch thick)
12 oz White mushrooms wiped clean (stem ends trimmed)
12 oz Stemmed spinach (rinsed and dried)
1/2 cup Loosely packed picked-fresh dill
For the vinaigrette:
Combine the vinegar, 1/2 cup plus 1 tablespoon of extra virgin olive oil, mustard, 3/8 teaspoon salt and 3/8 teaspoon pepper in a small bowl and whisk with a fork; set aside.
For the salmon:
Preheat the oven to 350°F. Line a baking sheet with foil. On the baking sheet, sprinkle the fillets on both sides with salt and pepper and let stand 5 minutes to allow the seasonings to absorb. Coat the fillets on both sides with about 1 teaspoon extra virgin olive oil each. Bake the salmon until medium-rare and just translucent in the center, 13 to 15 minutes. Let cool to room temperature, then refrigerate if not using immediately.
Cut a thin slice off the top of each mushroom cap to stabilize it. Set the mushrooms, cut side down on the cutting board and cut into 1/4-inch-thick slices.
In a large bowl, combine the spinach, sliced mushrooms, and dill. Give the vinaigrette a stir with a fork and add to the bowl. Break the salmon into pieces and add to the bowl. Season with a pinch more salt and pepper. Toss the salad very gently until everything is lightly coated with vinaigrette.