Beef Medallions with Saucy Shiitakes

Name: Beef Medallions with Saucy Shiitakes
Ingredients: 1 tablespoon, plus 1 1/2 teaspoons vegetable oil; 4 beef tenderloin medallions (about 4 ounces each), patted dry; 1/4 teaspoon kosher salt, plus more for seasoning; Freshly ground black pepper; 4 ounces shiitake mushrooms (about 12 medium), stemmed; 2 shallots, coarsely chopped; 1 clove garlic, minced; 1/4 cup Cognac or other brandy, or Madeira; 1/4 cup chicken broth, homemade or low-sodium canned; 3 tablespoons light sour cream; 1 tablespoon chopped fresh parsley leaves