1. Place all ingredients in a blender and blend until smooth.
2. Transfer to a saucepan and place on the stovetop over medium-high heat. Watch carefully, whisking every 30 seconds or so. As soon as it starts to bubble, remove from the heat (continued heat will cause the arrowroot to lose its thickening ability). Transfer to individual serving dishes (glasses or ramekins) and refrigerate for three hours; the pudding will thicken as it cools.
3. Serve with your choice of toppings.