Peel, quarter and core the apples. Cut apples into small pieces. Bring to the boil with 8 tbsp. sugar, apple juice and cinnamon stick. Simmer covered for 6-10 minutes. Let applesauce cool down. Remove cinnamon stick.
Peel, wash and finely grate the potatoes. Drain the potato mixture well in a fine sieve, collecting the starchy liquid. Peel and grate the onion and add to the potatoes. Carefully drain off the liquid that has been collected.
Add the potato starch to the potatoes. Add egg and additional potato starch (depending on how starchy the potatoes are). Season the potato buffer mixture with salt and pepper.
Smooth a little and fry for 3-4 minutes on each side. Drain finished buffers on kitchen paper. Serve immediately. Arrange potato pancakes with some sugar and applesauce on plates.