3 berry greutze Recipes

currants (assorted red fruits, in any combination) or 2 1/4 lbs raspberries (assorted red fruits, in any combination) or 2 1/4 lbs brambleberries (assorted red fruits, in any combination) or 2 1/4 lbs strawberries (assorted red fruits, in any combination) or 2 1/4 lbs sour cherries (assorted red fruits, in any combination) or 2 1/4 lbs plums (assorted red fruits, in any combination), sugar (or more to taste, depending on the tartness of the fruit), water, cornstarch, rum (optional), milk or cream, to serve with the dessert

frozen mixed berries , thawed reserving juice (strawberries, raspberries, blackberries, red currant, cherries etc.), fruit juice , preferrably cherry, including the reserved juice plus, fruit juice , preferrably cherry, sugar, cornstarch