Maww.
My wife just bought me a baked potato filled with mashed potato. It was good.
Take the potato, wash it, dry it, poke holes in it.
Put on a thin coat of oil, then kosher salt. Bake at 475 F for 1 hour directly on the oven rack (put a catch tray of aluminum -or aluminium for you brits-under to catch the oil that drips so you don’t have to clean the oven again)
This will give a baked potato with a nice crisp crust. Open the potato and scoop out the outside, mash with lots of butter until mostly smooth. Put back in potato skin and top with salt, pepper, and gravy or other sauce. Eat the mashed potato and then eat the crunchy and salty skin.