Salt Cod Cakes With Herbed Mayonnaise

Name: Salt Cod Cakes With Herbed Mayonnaise
Ingredients: 1 cup mayonnaise; 1 tablespoon coarsely chopped tarragon; 1 tablespoon coarsely chopped flat-leaf parsley; 1 tablespoon coarsely chopped chives; 1 pound skinless salt cod fillet; 3 cups milk; 2 cups diced (1-inch) peeled Idaho potatoes (about 3 medium); 2 tablespoons olive oil; 1 cup thinly sliced scallions (about 1 bunch); 1/3 cup heavy cream; 2 tablespoons coarsely chopped tarragon; Salt and freshly ground pepper; All-purpose flour, for dusting; Vegetable oil, for frying