In a bowl, combine cabbage and vinegar. Mix well to combine and set aside.
Combine shrimp, chili powder, lime juice and garlic. Mix well.
To a skillet, add oil on medium heat. Once hot, add shrimp in a single layer. Sear for 2-3 minutes per side, until shrimp is no longer pink.
Combine mayonnaise and lime juice in a small bowl.
To each plantain shell, add a handful of slaw, shrimp, and mayo-lime sauce. Garnish with fresh cilantro and jalapeno, if desired.