How to Make It
Rub the salmon with 1/2 tablespoon of miso. In a bowl, mix 1 1/2 tablespoons of lemon juice, 1 1/2 tablespoons of ginger and the sesame oil. Add the salmon and turn to coat; let stand for 10 minutes.
In a bowl, mix the remaining 1 tablespoon of miso with the remaining 1 tablespoon of ginger. Whisk in the remaining 1/4 cup of lemon juice and the soy, then whisk in the olive oil. Add the chives and season with pepper.
Light a grill or preheat a grill pan. Add the salmon, skin side down. Cover the grill and cook the salmon over a medium-hot fire for 4 to 6 minutes, depending on the thickness of the fillets. Flip the salmon and grill for 2 to 4 minutes longer, or until the salmon is just cooked through. Transfer the salmon to a plate and keep warm.
Arrange the spinach on a serving platter and top with the fillets. Drizzle with half of the vinaigrette and serve immediately, passing the remaining vinaigrette at the table.