Rinse your lingonberries and pick out any impurities.
Place clean lingonberries into a large cooking pot.
Stir in sugar and keep over medium to high heat.
Bring to a rolling boil. Reduce heat and simmer for at least 30 minutes or until it looks set. The jam will appear translucent.
Test if the jam is set by dropping some on an ice cold plate, the jam is ready if it doesn’t run. If it runs, keep for some more time to cook over low heat and repeat the test until it doesn't run anymore. AND/OR use a candy thermometer to determine if it's set, 220° Fahrenheit/ 150° Celsius.
Drop some rum into the lids. That will keep it clean.
Fill your jars with the hot lingonberry jam, close well with the lid and turn the jars upside down to create a vacuum.
When cooled, store in a cool and dry place.
1 serving = 1 Teaspoon, 70 servings = about 3 jam jars
Store them in a dry and cool place and keep away from direct sunlight. If you live in a humid tropical climate, please store the jam in the fridge. Also, store in the fridge once you opened your jar.
The jam will always appear liquid when cooking hot. It will set when it cools down, hence why we test with an ice-cold plate.