Mix first 4 ingredients and 4 1/2 teaspoons tarragon in medium bowl. Using moistened hands, divide mixture into 4 parts. Shape each into 1/2-inch-thick oval patty. Melt butter in heavy large skillet over medium-high heat. Add patties; saute until cooked through, about 4 minutes per side. Transfer to plates. Add broth, mustard and 1 teaspoon tarragon to skillet. Boil until gravy has reduced enough to coat spoon, whisking occasionally, about 5 minutes. Spoon over patties.