Filet of Beef With Mushroom and Tarragon Cream Sauce
Juice of 1 lemon
1/3 cup heavy cream
1/2 teaspoon kosher salt, divided
1 teaspoon plus 1/2 cup all-purpose flour, divided
1 teaspoon plus 1 tablespoon butter, divided
3 large boneless, skinless chicken breasts, (about 1 1/2 pounds), trimmed
1/4 teaspoon ground white pepper
1 teaspoon peanut or canola oil
1 cup reduced-sodium beef broth, divided, plus more as needed
8 oz sliced mushrooms
3 tablespoons finely minced fresh tarragon, or dill, plus sprigs for garnish
Combine lemon juice and cream in a small bowl. Season with 1/4 teaspoon salt. Mash 1 teaspoon flour and 1 teaspoon butter in another small bowl until a paste forms. Set both bowls aside.
Dry beef thoroughly with paper towels. Season with the remaining 1/4 teaspoon salt and white pepper.
Heat the remaining 1 tablespoon butter and oil in a 12-inch cast-iron skillet over medium-high heat. Add the beef—do not crowd the pan. Cook, turning once, until nicely browned on both sides, about 3 minutes total. Add 1/2 cup broth, reduce the heat and cover.
Simmer until the beef is cooked through, 3 to 4 minutes. (Check to make sure the pan juices don’t run dry. If necessary, add more broth, a tablespoonful at a time, to prevent scorching.) Transfer the beef to a clean cutting board and tent with foil.
Add the mushrooms and remaining 1/2 cup broth to the pan and bring to a boil over high heat. Cook until reduced to about 1/4 cup, 2 to 4 minutes. Reduce heat to medium, add the reserved lemon cream and bring to a simmer. Gradually whisk in the reserved butter-flour paste, a few bits at a time, until the sauce coats the spoon, 1 to 2 minutes.
Reduce the heat to low and return the beef to the pan along with tarragon (or dill). Turn to coat with the sauce and cook until heated through, 1 to 2 minutes. Serve with the sauce, garnished with sprigs of tarragon (or dill), if desired.