The day before you plan to assemble the turon, peel plantains and slice horizontally into 3” segments. Cut each of these segments in half lengthwise so each plantain yields 6 pieces.
Heat 1/2 cup oil in a large pan and saute plantain slices in batches, turning, until golden brown.
Remove plantains from the pan to a plate and allow to cool completely. Once all plantains are cool, cover and place in refrigerator overnight.
The next day, combine sugar and vanilla extract in a medium bowl. The mixture should be damp, but not wet. Beat an egg white in a small bowl, and have your lumpia wrappers ready.
Coat each plantain piece in the sugar/vanilla mixture then place on a lumpia wrapper. Roll plantain in lumpia wrapper, tucking in the ends. Seal each toron by brushing the edges with egg white. Repeat until you have used up all the plantain pieces.
Heat remaining 1/2 cup oil in a saute pan over medium high heat. Add turon to oil, careful not to overcrowd the pan, and fry until golden brown, turning occasionally. Drain turon on paper towels and serve hot.