Peel, cut up and slice enough Potatoes to put in desired Dish.
1stick Butter or Margarine (start with small chunks of butter/margarine)
Salt and Pepper to taste.
Put potatoes in pot to Boil, put on low to medium heat. Allow Potatoes to come to boil, the turn down if necessary to simmer. (You prepare like you would for making mashed or cream potatoes.)
Check with fork and see if potatoes are tender (you can break into with fork).
Pour off most not all the water. (You leave some to make the liquid.)
Now, stir adding chunks of Butter/Margarine until you make something that looks like gravy.
Add salt and Pepper to taste.
Be sure not stir any more than necessary make the liquid, you want to leave most of the potatoes whole.
(There are no set measurements. Mother learned cooking from her grandmother and Mother. They grew up at a time, when there was no cookbooks and you experimented until you got it right, then either remembered it, or took notes on whatever you had.)