Svenska and this strikes a familiar chord of my memory, I know I love dark and strong coffee but I am gonna give this a try
My mother used to boil coffee like this but her magic ingredient was an egg shell or two - ONLY the egg shell... NOT the contents. She would serve the eggs separately with delicious, strong coffee...free of coffee grounds which, with the egg shells, remained on the bottom of her coffee pot, not in our cups. If you need to try both methods, try this first.