In a medium saucepan, whisk together the cornstarch and granulated sugar until well combined.
Slowly pour in the full-fat oat milk while continuously whisking.
Place the saucepan over medium heat and continue to whisk the mixture as it heats up.
Once the mixture starts to thicken (after about 5-7 minutes), add the vanilla bean paste and the pinch of turmeric if using.
When the custard has reached your desired thickness, remove it from the heat.
Transfer the custard to serving dishes or a large bowl and allow it to cool at room temperature for a few minutes before covering with plastic wrap. Chill in the refrigerator for at least an hour before serving.
