Add potatoes to a pot of cold, salted water and bring to boil. Let boil for about 10 minutes, or until potatoes can be pierced with a fork. As soon as they are done, transfer to strainer and cover with ice to ensure they don’t carry over cook and start falling apart. Once dried, transfer onto a serving plate.
Combine sauce ingredients in a blender and blend on high until smooth. Add more milk as needed and adjust taste with salt if necessary.
Pour a generous amount of the cheese sauce over the potatoes.
Keep it simple and serve as is, or add hard boiled eggs.
You can also add pickled red onions and olives on top, a traditional way to serve them from Lima, Perú.