Scrub the potatoes gently in cold water, put them in a covered pot and fill with just enough water to cover them. Add a good handful of salt and the dill stem, gently bringing the potatoes to a boil with the lid on.
Skim off any white foam or other impurities once the water starts to boil. Lower the heat and boil for 5-7 minutes.
Remove the potatoes and serve with chopped dill, a slab of cold butter and sea salt.