One-Pan Steak with Potatoes, Mushrooms, and Asparagus

Ingredients

• 1/2 cup sour cream
• 2 tablespoons prepared horseradish
• 2 tablespoons water
• 3 1/4 teaspoons kosher salt, divided
• 1 1/4 teaspoons pepper, divided
• 2 (1-pound) strip steaks, 1½ inches thick, trimmed and cut in half crosswise
• 3 tablespoons unsalted butter, divided, plus 1 tablespoon melted
• 1 pound Yukon Gold potato, unpeeled, cut into ¾-inch pieces
• 12 ounces cremini mushrooms, trimmed and quartered
• 1 shallot, halved and sliced thin
• 3 garlic cloves, sliced thin
• 1 tablespoon chopped fresh thyme
• 1 pound asparagus, trimmed