At the bottom of the jars, put the black pepper and mustard seeds. Add the salt, sugar and vinegar.
Then arrange the pickles, while taking care not to leave any space between them. Once the jars are filled, add a few slices of onions on top, as well as a sprig of dill.
Add an aspirin to every jar. Finally, top off the jars with boiling water and seal immediately. Turn them over with the caps facing down.