Between sheets of waxed paper, pound breasts to 1/4-inch thickness. Dust with flour. In shallow bowl, whisk together egg white and water. Combine almonds and bread crumbs and place on a plate.
In nonstick skillet sprayed with vegetable spray, heat oil over medium-high heat. Dip breasts in egg wash, then in crumb mixture. Cook for 3 minutes on one side; turn and cook for 2 minutes longer or until just done at center.
Meanwhile, in small saucepan whisk together mayonnaise, sour cream, mustard and tarragon; heat over low heat just until warm. Serve over chicken.