The only trick to making good causas is you need to get in there and really knead the potatoes.
1 Mash the drained, cooked potatoes by hand or press them through a ricer. Mix in the other ingredients.
2 Leave the potato base in the bowl or turn it out onto a work surface, add the ají amarillo paste and lime juice, and knead the potatoes with the base of your hand for several minutes. Drizzle the olive oil on top and knead the potatoes for 2 to 3 minutes more, until smooth. (If you are making beet or spinach causas, add the puree and continue to knead until well incorporated.)
3 If making sushi-style or cut-out causas, spread the potato base on a rimmed baking sheet. If making molded causas, place the potato base in a bowl. Cover and refrigerate overnight.
4 Cut or mold the causas however you would like and add your toppings.