Cook the potatoes: Add to a pressure cooker with enough water to cover the potatoes. Close the lid and pressure cook for 6 mins, let the pressure release naturally.Saucepan: Add potatoes and tap water(about an inch over the potatoes) to a saucepan. Bring to a boil over medium heat. Continue to cook for 25 mins or until tender.
Drain the potatoes for 5 mins. Brush oil on baking sheet, place potatoes and press with fork or potato masher to flatten to about ¼ inch thick.
Brush oil on the potatoes. Sprinkle salt and pepper generously. (you can also add minced garlic and herbs). Bake at 400 deg F (205 C) for 25 to 30 mins.
Meanwhile process the chimichurri ingredients in a food processor or blender with a few tbsp of water until coarsely blended. Taste and adjust flavor with salt, lime.
Take the potatoes off the baking dish and serve hot, dressed with chimichurri.To make ahead: Boil the potatoes, flatten, cool and refrigerate for upto 3 days. Make the chimichurri and refrigerate in a closed container for upto 3 days
