Heat oven to 400 degrees. Heat 1 tablespoon of the oil in a large ovenproof skillet over medium-high heat. Season pork with 1/4 teaspoon of the salt and pepper to taste.
Cook, turning, until browned, 5-6 minutes. Transfer skillet to the oven. Roast until pork is cooked through, 12-15 minutes. Let rest 5 minutes before slicing.
Meanwhile, on a rimmed baking sheet, toss asparagus, shallots, 1 tablespoon of the oil, remaining 1/4 teaspoon of the salt and pepper to taste. Arrange vegetables in a single layer. Roast, tossing once, until tender, 12-15 minutes.
Whisk together vinegar, mustard and remaining 1/3 cup of the oil. Slice pork; serve with vegetables. Drizzle all with vinaigrette.