Place the chicken breasts between two pieces of waxed paper. Pound to 1/2" thickness using a meat mallet. Set aside.
Place egg whites and tarragon in a shallow bowl. Beat with a fork until frothy. Combine flour, garlic powder, cornstarch and baking soda in another shallow bowl and mix well. Dip the chicken in flour then egg white mixture and turn to coat. Dip in flour again and coat completely.
Heat the oil to 350 F in a deep medium skillet. Add 2 chicken breasts to the skillet. Cook, turning once, until golden brown and cooked through, about 7-10 minutes. Drain on paper towels. Repeat with remaining chicken.