Heat oven to 400° F.
Heat 1 tablespoon of the oil in a large ovenproof skillet over medium-high heat.
Season the pork with 1/4 teaspoon each of the salt and pepper. Cook until golden brown, 3 minutes per side. Transfer skillet to oven and roast 18 minutes. Transfer the pork to a cutting board and let rest at least 5 minutes before slicing.
Meanwhile, place the asparagus on a baking sheet in a single layer. Scatter the shallots over the top. Drizzle with 1 tablespoon of the oil, season with the remaining salt and pepper, and roast until cooked through, 12 to 15 minutes.
In a small bowl, whisk together the mustard, vinegar, and the remaining oil. Divide the pork and asparagus among individual plates and serve with the vinaigrette.
Tip: When the weather turns warm, take this recipe outside. Heat a grill to medium and cook the pork, covered, turning occasionally, for 20 minutes. Grill the shallots (cut in half) and asparagus, turning occasionally, for 8 to 10 minutes.