Add the sauce ingredients to a saucepan over low heat (except the vanilla). Allow the mixture to melt and thicken for 2-4 minutes, continuously stirring and making sure the chocolate isn't burning. Once it has thickened, remove from heat and stir in the vanilla.
Pour the ice into a cup, then add the oat milk over top. Pour the coffee on top of this.
Then pour the white chocolate mixture over top of this, and gave it a stir.
Top with vegan whipped cream (optional, but of course recommended!)