Peel and core out the pineapple. Slice the meat of the pineapple into three-quarter-inch-thick slices. Collect all the juice that emerges and reserve. Optional: If you have a juice extractor, cut the core into chunks and run it through the machine to get all that juice.
In a large, heavy skillet over medium-high heat, heat half the butter until it bubbles. Add the pineapple slices in one layer, and brown them around the edges on each side. Remove and reserve, keeping all the juice in the pan.
When all the pineapple slices are browned, lower the heat to medium-low. Add the remaining butter, the brown sugar, and all the pineapple juice. Bring to a light boil, stirring lightly to dissolve the sugar. Allow the sauce to thicken to about the consistency of cane syrup.
Return the pineapple slices to the pan (you can put them all in there now). Sprinkle the peppercorns over the pineapple and stir lightly to distribute
(Optional.) Measure the rum into a glass and pour into the pan. (Never pour spirits directly from the bottle into a hot pan.) Bring to a boil, and if you like and if your kitchen is safe for flames, touch a flame to the pan and flambee the pineapple. Let the flames die down and remove from the heat.
Serve the pineapple slices over the ice cream and top with a generous amount of sauce.
