In a blender or food processor, combine the aji amarillo paste, evaporated milk, queso fresco or feta cheese, saltine crackers, minced garlic, and vegetable oil. Blend until you achieve a smooth and creamy sauce. If the sauce is too thick, you can add a little more milk to reach the desired consistency. Season with salt and pepper to taste.

Slice the boiled potatoes into thick rounds or halves, depending on your preference. Arrange the potato slices on a serving platter lined with lettuce leaves.

Pour the Huancaina sauce generously over the potatoes, making sure each slice is covered. You can reserve some sauce for serving on the side if you like.

Garnish the dish with slices of hard-boiled eggs and black olives.

Serve the Papas a la Huancaina at room temperature or chilled. It can be enjoyed as an appetizer or a side dish alongside grilled meats.