Step 1) Trim fat from chicken. Rinse; pat dry with paper towels. Place chicken between two sheets of plastic wrap. Flatten slightly using smooth side of meat mallet until 1 to 1 1/2 inch thick.
Step 2) Place 2 tablespoons flour in a large resealable plastic bag. Add chicken and shake to coat. Add egg and shake to coat.
Step 3) Combine bread crumbs, seasoning salt, pepper and tarragon in a shallow bowl. Roll chicken in mixture.
Step 4) Heat 2 tablespoons oil in a large nonstick skillet over medium heat, swirling to coat bottom of skillet. Cook chicken 4 to 5 minutes. Flip and add remaining 2 tablespoons of oil and swirl to coat pan. continue to cook chicken until browned and no longer pink in center. Transfer chicken to platter; cover to keep warm.
Step 5) Combine milk and 1 tablespoon flour in measuring cup. Stir until smooth; set aside.
Step 6) Add gravy to skillet. Stir in milk and flour mixture; whisk thoroughly. Cook over medium heat until thick and bubbly, 2 to 3 minutes, stirring occasionally. Add garlic salt and pepper to taste. Serve with chicken.