Wash, clean and cut the strawberries into pieces. Mix with sugar and citric acid in a large pot. Cut the chocolate into small pieces. Bring strawberries to the boil while stirring over high heat. Cook for 4 minutes while stirring continuously until bubbly.
Fold in chocolate. Fill jam into the prepared, clean glasses and close them. Place glasses on the lid for about 5 minutes, turn them over again and let them cool down. Jam keeps in a cool place for 3-4 months