The classic Joël Robuchon mashed potatoes uses a ratio of potatoes butter 3 to 1. Avoid peeling off potatoes prior cooking; it will absorb less water with skin left on. It also prevents vitamins and minerals from being bleached in the cooking water. In addition to that the potato peels contribute to the overall potato flavor and taking the peels off after cooking is faster and easier. Choosing the proper potatoes is crucial. There are basically three types of potatoes: Starchy like Russets, waxy like Red Bliss, and somewhere in between; Yukon Golds. Avoid the use of the waxy, red potatoes for your mash. They just won't break down enough and absorb the dairy very well. Russet will give you the smoothest mash, but I prefer the flavor, texture, and color of Yukon Golds. The Ratte fingerling is a small potato with a unique nutty flavor and smooth, buttery texture; the ultimate choice for this recipe. The variety originated in Denmark or France in the late 19th century and is a favorite of French chefs, including Joël Robuchon who used them to make his world famous potato puree. In addition to pick the best potatoes, use the best butter as well.
Place unpeeled potatoes into a large saucepan. Add water to cover, add a pinches of salt. Bring to a boil and cook on low. Depending on the size, Ratte fingerling potatoes should take 25 minutes to cook. Test a potato for doneness with a toothpick. Remove from water and peel while still hot holding potato up with a fork. In a saucepan pass hot potatoes through the food mill or potato ricer. For a silkier result, work purée over low heat with a spatula. Add the cubed butter gradually continuing stirring constantly. Season with salt to taste. Whisk in warm milk vigorously to smooth it out. Pass potato purée through a fine mesh sieve. Enjoy!