Bake potatoes at 400 °F until a fork easily pierces, about 45-60 minutes.
Let the potatoes cool to a handle-able temp, but you do want to do this while they're warm. Once they get cold they are harder to scoop and mash.
Cut the potatoes into halves lengthwise, and scoop all the insides into a medium sized bowl. Add in the ham, cream cheese, milk, rosemary and mash well. Salt and pepper to taste.
Fill each potato level with the filling.
You can immediately bake them until browned on top (450 °F for 15 minutes) OR we like to freeze and use on busy days.
To bake from frozen, bake at 400 °F until browned on top.
Notes
*Amount of milk used depends on how dry your potatoes are. Go slow and don't add it all right away.
Fill the potato skins level so that you have enough filling for all. Or you can mound them for a fancier presentation, and enjoy the leftover skins by brushing with butter before baking to a crisp.