Steam the fiddleheads over boiling water for 5 minutes,or until they are crisp-tender. Drain, then chill in a bowl of ice and cold water to stop the cooking. When they have cooled transfer to colander to drain.

In a small bowl whisk together the yogurt, mayonnaise, lemon juice, mustard, ramps. Add salt and pepper to taste, whisking until the sauce is smooth. Serve the Fiddleheads topped with the sauce.