Wash the elderberries and put them dripping wet with stems in a large pot. Put a lid on it and let it boil quietly at medium heat for 20 to 25 minutes. In the meantime rinse glasses in hot water.
Cut the preserving cellophane to size. Peel and halve the pear, remove the core. Cut pear halves crosswise into thin slices. Pass the elderberries through a fine sieve or cloth. Measure out one litre of juice.
Put juice and jam sugar in a pot and mix well. Add pear pieces and lemon juice. Bring everything to the boil over a high heat, stirring constantly, and let it boil for one minute (after the clock) until it becomes bubbly.
Remove the pot from the stove and pour the jelly hot into glasses. Glasses must be filled to the brim. Close them immediately with moistened cellophane. Makes 4 glasses of 3/8 litres each.