Pour heavy whipping cream into a saucepan and bring to a low simmer over low heat; add cardamom, vanilla bean seeds, and the vanilla bean pod to the simmering cream.
Remove saucepan from heat and stir white chocolate chips into the cream; stir continually until the chocolate has melted and the mixture is smooth.
Return saucepan to low heat. Cook the sauce, stirring frequently, until thick, 10 to 20 minutes. Strain through a very fine mesh strainer into a bowl.
Let sauce cool for at least 10 minutes before serving.
