Steak Salad with Horseradish Dressing

Name: Steak Salad with Horseradish Dressing
Ingredients: 1/2 cup sour cream; 3 tablespoons prepared horseradish; 1 tablespoon chopped fresh chives; 1 teaspoon honey; 1 teaspoon red wine vinegar; Kosher salt, freshly ground pepper; 2 tablespoons olive oil, divided; 1 1-pound rib-eye, flank, or skirt steak; 12 ounces fingerling potatoes, thinly sliced; 1/2 English hothouse cucumber, thinly sliced; 6 radishes, cut into thin wedges; 2 cups greens (such as arugula or torn Bibb lettuce leaves); Pickled Red Onions