Into a large bowl, press the cooked potatoes through a ricer (or mash the cooked potatoes) and mix with the oil, chili paste, and 1 tablespoon lime juice. Mix well, season with salt to taste, and set aside.
Cut the red onion into slices. To blanch the onion, fill a small pot with water and add 1 tablespoon salt. Bring to a boil and add the onion slices; boil for 1 minute. Meanwhile, fill a medium bowl with ice water. Remove the onion from the pot and place in the ice water for 2 minutes. Drain, dry with paper towels, and chop finely. In a small bowl, mix the onion, mayonnaise, and remaining lime juice and set aside.
To make the causa rellena, place 1/2 cup of the potato mixture into each of 4 individual ring molds, cover with a layer of the mayonnaise-onion mixture, top with a layer of avocado slices, add 5 shrimp and top with the remaining potato mixture. Unmold each causa onto a small plate and top with the remaining avocado slices, shrimp, hardboiled egg, and olives. Garnish with lettuce leaves.