This is a reliably easy dish that always shows up at gatherings of my Peruvian hubby's family and friends. Potatoes come from Peru, after all, and this is the most common dish that you'll see, simple and delicious, as well as attractive to the eye. The story is, that in the little town of Huancaina in the mountains of Peru, a well-loved local cook had run out of most of her kitchen supplies and had to make a quick dish to feed hungry workers on the plantation, and this is what she came up with--one of those "whatever is left in the kitchen" recipes that just grew and grew in popularity. I am a Southerner by birth and come from a family that usually looks askance at "foreign" cuisine, but even they love this tasty dish! The sauce is so good you can add it too cooked pasta or pour over macaroni, add canned salmon or tuna and bake it into a delicious casserole the next day! —BeijingRose
Boil your potatoes in salted water until tender--Leave the skins on! This keeps the vitamins and flavor of the potatoes intact. Pierce with a fork to check if they are done--usually about 30 minutes. Rinse in cold water and peel off the skins. LET THEM COOL in the fridge for an hour before cutting into thick slices. Set aside.
In a blender mix the evaporated milk, oil, crumbled white cheese (in a pinch, if you can't find Queso Fresco, you can use cream cheese),aji amarillo and a pinch of salt, then crumble the crackers and add them one handful at a time. Blend at medium speed, stop and start. What you want is a slightly thickened sauce, not TOO thick--this sauce thickens when you refrigerate it.
Refrigerate your sauce for at least 2 hours. Arrange the lettuce leaves around the bottom and sides of a large baking dish (glass looks best), layer the potato slices, pour on enough sauce to mostly (but not entirely) cover the potatoes, then garnish with sliced eggs and olives and sprigs of fresh cilantro.