Retrograde potatoes is a modernist cuisine method to make the best possible mashed potatoes. 1st you simmer the sliced potatoes in 70-71C water for 30mins, then drain, rinse to cool, and simmer them until done. After that mash into a ton of butter, 50% ratio :) This low heat pre simmering somehow locks the starch molecules so they dont turn into glue even when beaten heavily with a whisk.
I was googling around and noticed that this retrograde mashed potatoes is used by ones suffering from diabetes also, it seems that they spike insulin less than regular mash. I dont know the science behind this, or even if this is correct, i must check somehow. Better mash and lower insulin spike, thats a win-win almost ;)