Mix together all ingredients except for romaine lettuce leaves, plantain chips, sweet potatoes, jalapenos, lime and lemon wedges and cilantro sprigs, in a bowl and marinate for 24 hours. Spoon ceviche into martini glasses. Place sweet potatoes on a plate. Place martini glass on plate with sweet potatoes. Place 1 slice of jalapeno, lime and lemon wedge on the sweet potatoes and garnish with a sprig of cilantro. Place romaine leaf and plantain chip in the ceviche.