Potato Crusted Salmon with Chive and Scallion Sauce

Name: Potato Crusted Salmon with Chive and Scallion Sauce
Ingredients: 1 large potato, peeled; One 12-ounce piece of salmon, skin on; 2 tablespoons spicy brown mustard; 1 tablespoon extra-virgin olive oil; Dash of salt; Pinch of pepper; 2 scallions, thinly sliced; 1 teaspoon extra-virgin olive oil; 1 teaspoon garlic, finely chopped; 1/8 cup champagne or rice vinegar; 1/4 cup dry white wine; 1/4 cup evaporated skim milk; 1/2 teaspoon cornstarch, mixed with 1 teaspoon of water; 3 chives, finely chopped; Salt and pepper, to taste