The ingredient list for this classic Peruvian dish may seem like an odd combination, but the end result is pure, comfort food (think the flavors of potato salad). Causa is comprised of layers of seasoned mashed potatoes, mayonnaise, hard-boiled eggs and olives. Most also include the addition of other ingredients and there seems to be as many variations as there are households in Peru. Some other traditional additions to the filling for causa are tuna, shredded chicken, bay shrimp, crab, chopped tomato and sliced avocado (any of these additions can be added to the mayonnaise and spread over the first layer of potatoes).
Add the potatoes to a large pot, cover with cold water and bring to a boil. Cook potatoes until soft, about 15 - 20 minutes. Drain the potatoes and pass them through a potato ricer or mash until very fine. Set aside and let the potatoes cool.
In a large bowl, mix cooled potatoes with olive oil, Aji Amarillo paste, lime juice and salt. Taste and readjust seasoning, adding salt and lime juice if necessary. Smooth half of the potato mixture evenly into a 13x9-inch baking pan. Next, spread the potato layer with mayonnaise and top with the chopped eggs, chicken and olives. Evenly spread the remaining potato mixture over the filling, making sure to smooth the top. Cover the pan with plastic wrap and refrigerate until cool, about 1 hour or overnight.
To serve, slice the causa into squares and garnish with sliced avocado, sliced bell peppers or parsley.