Whisk together the milk, egg, brown sugar, flour, and salt in a shallow dish until well blended. If the batter is too thick you can add additional milk.
Heat the oil (about ½-inch deep) in a skillet over medium heat.
Dip each slice of plantain in the batter, coating completely and letting any excess drip off. Add the battered plantain slices to the hot oil, in batches if needed.
Cook, 2 minutes per side, or until golden brown. Remove from the oil and let drain on paper toweling.
Serve warm.
