Preheat oven to 400°.
To prepare cream puffs, lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, 2 teaspoons sugar, and 1/4 teaspoon salt; set aside. Combine 1 cup milk, butter, and espresso granules in a large saucepan; bring to a boil. Reduce heat to low; add flour mixture, stirring well until mixture is smooth and pulls away from sides of pan. Remove mixture from heat. Add eggs and egg white, 1 at a time, beating well with a wooden spoon until smooth.
Drop the dough by level tablespoons, 2 inches apart, onto baking sheets coated with cooking spray. Bake at 400° for 10 minutes. Reduce oven temperature to 350°; bake an additional 10 minutes or until browned and crisp. Remove from oven; pierce the side of each cream puff with the tip of a sharp knife. Turn oven off; let cream puffs stand in partially closed oven for 20 minutes. Remove from baking sheet; cool completely on a wire rack.
To prepare pastry cream, sprinkle gelatin over water in a small bowl; set aside. Combine 3/4 cup milk and next 5 ingredients (milk through egg yolks) in a medium saucepan. Place over low heat; cook until warm, stirring constantly. Stir in gelatin mixture; cook over medium heat until thick (about 8 minutes), stirring constantly. Remove from heat. Place pan in a large ice-filled bowl; let stand 15 minutes or until room temperature (do not allow mixture to set). Remove pan from ice. Gently whisk in whipped topping. Cover and chill 4 hours or until thick.
Cut tops off cream puffs; fill each cream puff with 1 tablespoon filling. Sprinkle with powdered sugar, if desired.