1. In a medium heatproof bowl, combine all ingredients except vanilla bean paste. Set bowl over a saucepan of simmering water and stir mixture occasionally until it is completely smooth and the white chocolate is melted. Remove bowl from heat and stir in vanilla bean paste.
2. Let cool for five minutes and then serve warm over ice cream. Store leftovers in an airtight container in the refrigerator for up to one week; rewarm gently before serving.