1 cup apple juice (also would be good with pear juice, peach nectar, etc)
1 teaspoon vanilla extract
1 1/2 tablespoons kuzu (aka kudzu, a starch used as a thickener in Japanese cooking)
Combine all ingredients in a small saucepan. Stirring constantly with a whisk, bring to a boil and continue stirring until mixture thickens and becomes more translucent. Eat warm or cold.