In a small skillet, heat the 2 tablespoons of vegetable oil and, over medium heat, sauté the onion, garlic and aji amarillo until the onion is translucent, about 5 minutes.
Remove onion mixture from the heat and in a blender or a food processor fitted with a steel blade, blend together with the crackers, white cheese, evaporated milk and salt, adding just enough vegetable oil to give the mixture a smooth creamy consistency.
Add the juice of 1/2 Key lime and blend for a few seconds more. Adjust seasoning to taste, adding more salt if necessary. Let sauce cool to room temperature or chill in the refrigerator.
To serve, pour the sauce over sliced cold boiled potatoes and garnish with boiled egg slices, olives, cooked corn kernels and lettuce leaves.Makes 6 Source: