Mix tempura mix and water together to form batter; do not overmix. Dip banana pieces into batter, then roll in panko to coat. Deep fry in hot (350 degree) oil until golden brown and crispy. Serve with 2 scoops rum-raisin ice cream and 1/4 cup Caramel Candy Sauce.
To make Caramel Candy Sauce: In sauce pan, bring butter to boil; boil 1 minute. Stir in brown sugar. Bring to boil; boil 1 minute. Add water; boil 30 seconds. Add cream and corn syrup. Bring to boil; boil vigorously 10 minutes. Remove from heat. Mix in vanilla extract. Cool; refrigerate, covered. Heat over double boiler to serve.