Why does the recipe instruct to leave skin on while boiling potatoes and then peel? Is there an added benefit to this? Seems odd to have to let po...

A cooked potato slips out of its skin; a raw potato clings to its skin, so if you peel it first, in addition to risking a waterlogged potato, you get less mashed potato. The more people you are cooking for the more this matters. I learned this from my mother in law (my husband has seven brothers). I usually eat the skin myself.

The less water, the more cream, milk, butter can be soaked up by the potatoes. Similarly, many recipes tell you to put your boiled potatoes back into the pot, minus the water, and then turn on the heat to evaporate the excess water.

If you use a food mill to rice your potatoes, it will peel them as it mashes. There's no need to let the potatoes cool.

The only reason to let them cool is to allow you to handle them. If you have a food mill, you can put them in hot and unpeeled; the mill will separate the skin from the flesh.

If you leave the skin on the potato flesh doesn't get water saturated, so holds up better with the mix-ins.