Broiled Mustard-Crusted Flounder

INGREDIENTS

• 4 boneless flounder fillets (1 1/2 pounds total)
• 1/3 cup low-fat plain Greek yogurt
• 1 teaspoon Dijon mustard
• 1 1/2 teaspoons capers, rinsed, drained, and roughly chopped
• 4 teaspoons extra-virgin olive oil, divided
• Salt and pepper
• 4 ounces tender greens, such as baby arugula, mache, parsley or chervil (4 cups)