1. Place chicken between 2 sheets of plastic wrap. Pound to about 1/2-inch thickness. Sprinkle with 1/4 teaspoon salt and 1/8 teaspoon pepper.
2. Dredge chicken in flour, shaking to remove excess. Heat butter in a large nonstick skillet over medium heat. Add chicken in 2 batches and cook until golden brown and cooked through, about 2 to 3 minutes per side. Transfer chicken to a serving platter; cover and keep warm.
3. Add wine and broth to skillet; simmer until boiled down to 1/4 cup. Stir in cream, custard, and remaining salt and pepper and cook 1 minute more. Stir in tarragon. Pour sauce over chicken. Makes 6 servings.