Salmon with Spinach

Prep time: 10 minutes | Cook time: 15 minutes | Serves 63 tablespoons unsalted butter2 pounds (907 g) fresh baby spinach4 shallots, minced6 salmon fillets3 tablespoons fresh lemon juiceSea salt and freshly ground black pepper, to taste2 teaspoons finely chopped fresh rosemary leaves6 lemon wedges, for garnishHorseradish cream sauce, for garnish Preheat