Ají amarillo chile paste lends this interesting uncooked Peruvian sauce a sunny hue and heat. The simple dish looks especially dramatic when made with purple potatoes. Slideshow: More Latin American Recipes
In a medium saucepan, cover the scrubbed potatoes with cold well-salted water. Bring to a boil, then reduce the heat to moderate and simmer until the potatoes are tender, 20 to 25 minutes. Drain well, and set aside to cool
Meanwhile, combine the queso fresco, milk, chile paste and garlic in a blender or food processor and process until very smooth. Season to taste with salt. Set aside.
When the potatoes are cool enough to handle, peel them and cut them crosswise into 1/2-inch-thick slices. Arrange the potatoes on a serving platter and drizzle with the sauce. Sprinkle with the olives, scallions and cilantro and serve.
The sauce can be made up to 1 day ahead and stored in an airtight container in the refrigerator.