Heat oil to 350°F in a deep fryer or large deep skillet.
While oil is heating, peel and thinly slice plantains lengthwise. or cut in long diagonal slices.
Divide slices in 2 or 3 batches to avoid overcrowding. Fry slices 3 to 4 minutes until golden. Remove using tongs and place on paper towels to drain.
Sprinkle lightly with cinnamon sugar. Turn to coat both sides. Serve immediately.
RECIPE NOTE: These crisp plantains are great as a snack and also work as a delicious garnish for ice cream.