Put a plate in the refrigerator and let it get cold. You will use the plate to test whether the jam is thick enough. Sterilize and cover the jars until use (see sterilization tips).
Peel pears and remove the seeds. Also, remove the stems. Cut the pear into cubes of about ½ x ½ inch (1 x 1 cm)
Combine pears with butter, sugar, and spices in a large pan. Mix everything well.
Bring to the boil, and then turn the heat low. Simmer for 1½ hours. Make sure you stir now and then. Check if the jam has thickened enough. Put a drop on a small cold plate and see if it sets immediately. If not, cook an extra five minutes and check again. Put the plate in the refrigerator in between so that it stays cold.
Optional: This jam contains chunks of pear. If you want a smooth sweet jelly or smaller pieces, use a food processor or an immersion blender (and if you don’t have a potato masher) to get rid of the pear pieces.
Pour ½ inch (1 cm) of jam into the jars and wait 1 minute. Then fill the jars and turn the lid on. Turn the jars upside down and let them cool to room temperature.