Avocado Shrimp Rolls

Name: Avocado Shrimp Rolls
Ingredients: 1 1/2 pounds Poached Shrimp, cut in 1/2 lengthwise, recipe follows; Tarragon Mayonnaise, recipe follows; 1/4 cup finely diced fennel; 6 rolls; 1/4 cup butter, softened; 1 avocado, sliced, see Cook's Note*; Preheat broiler.; 1 1/2 pounds raw shrimp, peeled, deveined, tail removed; Kosher salt; 6 black peppercorns, whole; 2 egg yolks; 1 tablespoon Dijon mustard; 2 tablespoons lemon juice; 1 cup vegetable oil; 1 teaspoon kosher salt; 1 teaspoon chopped fresh tarragon leaves