Place the onions, chile pepper and lemon juice in a large mixing bowl and set aside to marinate.

Bring a medium pot of water up to a boil, add the shrimp, and cook until just opaque, about 3 minutes. While the shrimp cook, prepare an ice bath, then immediately shock the shrimp in the ice water to stop the cooking. Add the reserved shells and tails to the water, turn off the heat, and allow them to steep.

Drain the shrimp, pat them dry, then slice into bite sized pieces. Add to the bowl with the onions, chiles and lemon juice, mix, then let marinate for about 15 minutes in the refrigerator. Leave the shrimp shells soaking in the water while it cools.

When the water is no longer screaming hot, strain out the shells and add 3 cups of the poaching liquid to the shrimp, along with the ketchup, orange juice, salt, cilantro and stir until thoroughly combined.

When ready to serve, heat about 1 inch of oil in a heavy bottomed pan or a deep fryer to 375 degrees. Use the large holes of a box grater to coarsely grate the plantains. Working in batches, drop the grated plantains into the hot oil, and cook, stirring occasionally until golden brown and crisp. Remove with a slotted spoon and place on paper towels to drain. Sprinkle with salt, then repeat with the remaining plantains.

To serve, ladle the ceviche into bowls, being sure to include plenty of liquid. Sprinkle with fried plantains and serve ice cold, with the remaining plantains on the side.