Combine first 5 ingredients in a heavy saucepan. Cook over medium heat, stirring constantly, 11 minutes or until sugar dissolves and mixture comes to a simmer (do not boil). Cool 5 minutes.
Beat yolks and banana extract in a medium bowl. Gradually stir about 1/4 of hot whipping cream mixture into yolks, and add to remaining hot whipping cream mixture, stirring constantly. Pour whipping cream mixture through a wire-mesh strainer, discarding banana solids.
Pour custard mixture evenly into 8 (8-ounce) ramekins or custard cups. Place ramekins in a large roasting pan; add hot water to pan to a depth of 1 inch. Bake at 350° for 35 minutes or until set. Remove ramekins from water, and cool slightly on a wire rack. Cover and chill at least 8 hours.
Place ramekins on a baking sheet; sprinkle 2 teaspoons sugar evenly over each custard. Broil 5 inches from heat until sugar is completely melted and caramelized (about 1 to 3 minutes). Garnish, if desired. Serve immediately.
Note: To prepare caramelized sugar pieces, combine 2 cups sugar, 1/2 teaspoon corn syrup, and 1/2 cup water in a heavy skillet. Cook over low heat, stirring until sugar dissolves. Increase heat to high, and cook until sugar is golden brown and registers 310° (hard crack stage) on a candy thermometer. Carefully pour onto a greased, foil-lined baking sheet. Cool and crack into pieces.