Place the milk and vanilla in a saucepan.
Bring the mixture to near boiling point over low/medium heat.
Place the egg yolks, maple syrup and arrowroot in the bowl of a kitchen stand mixture (or using an electric hand whisk) and whisk on medium until pale and thick. This may take 3-5 minutes.
With the whisk still on, gently pour the almost boiling milk mixture into the bowl. Do this by pouring the hot liquid down the sides of the bowl.
Return to combined mixture to the saucepan and whisk continually over medium heat until boiling. Continue whisking the boiling mixture for 1 minute.
Serve immediately or pour the custard into a heat proof bowl and allow to cool. Cover with plastic wrap and refrigerate until ready to use. The custard will thicken upon cooling.