Add the apples, cranberry juice, sugar and cinnamon to a saucepan. Bring to a boil over high heat. Reduce heat to low, cover, and simmer until the apples are very soft, about 10 minutes. Dissolve the potato starch in 1 cup cold water. Pour this slurry into the hot apple mixture, stirring constantly. Continue stirring until the kissel starts to bubble again, about 1 minute. Remove from the heat and pour into individual dessert dishes. Allow them to cool then refrigerate them for at least 2 hours.
In a small bowl mix the sour cream with the brown sugar and lemon juice. To serve, put a good dollop of the sweet sour cream on top of the kissel and swirl it in with a spoon. Garnish with the crushed gingersnaps.