The original recipe calls for fresh fruit, however, I have successfully made this with frozen fruit. I used two bags of mixed berries from Trader Joe’s, and also substituted unsweetened cranberry juice for the prune or cherry juice. Test the sweetness before adding the fruit – this is a somewhat tart fruit sauce, so you may want to add more sugar if you prefer things on the sweet side. Also, this recipe makes quite a large amount – you may want to cut it in half if you are making it for a smaller group.
Put cornstarch in a small bowl, whisk in 1/4 c water to make a lump free slurry. Pour juice into a heavy 4 quart pot and add the sugar and flavorings (lemon peel, and/or vanilla, and/or cinnamon) set over medium heat and stir until the sugar has dissolved. Add the fruit and bring to a boil.
Give the slurry another wisk and pour into pot just as the fruit mixture starts to bubble. The grutze will start to thicken almost immediately. Bring it back to a boil and then remove the pot from the heat. If using vanilla bean remove it from pot.
Pour the hot pudding into a large serving bowl or into individual dishes and let cool completely before refrigerating overnight. Serve cold over vanilla ice cream or pudding.
Adapted from My Berlin Kitchen