As classic as a sauce can be, this one needs to live up to its name. Elevate a steak or roast with this pan sauce that was named for that center cut of a beef Tenderloin.
Melt 1 tablespoon butter in 12-inch nonstick skillet over medium heat until hot. Add shallots, cook 2 minutes until golden brown, stirring often. Add mushrooms and garlic; cook for 3 to 4 minutes until mushrooms are tender, stirring often.
Stir in wine; simmer 7 to 8 minutes. Add broth and bring to a boil; simmer 15 to 20 minutes until the liquid has reduced by half. Whisk in remaining 2 tablespoons butter; stirring until the butter is incorporated. Stir in tarragon leaves. Season with salt and pepper, as desired.