Danish Creamery : Grilled Cod with Smoked Brown Butter Vinaigrette

Ingredients

• 1 small shallot, very finely chopped
• 1 teaspoon Dijon mustard
• ¼ teaspoon fine sea salt
• freshly ground black pepper
• 4 ounces (1 stick) Danish Creamery Butter, smoked (see first step)
• ¼ cup fresh lime juice (about 4 limes)
• 2 teaspoons minced tarragon leaves
• 1 ½ pounds fresh cod filet, cut from the larger end (about 1 inch thick), very cold
• 3 Tablespoons mayonnaise
• ½ teaspoon kosher salt
• ¼ teaspoon ground black pepper
• 5 cups mixed baby greens