Any dairy free milk works well here. Full fat canned coconut milk creates the richest result, while cashew milk and almond milk are excellent lighter options. Avoid rice milk as it may not set up as firmly.
The peanut butter adds a subtle richness that enhances the chocolate flavor. Feel free to substitute almond butter, sunflower seed butter, or omit entirely.
Adding chopped dairy free chocolate makes the pudding thicker and gives it a more intense chocolate flavor. It is optional but highly recommended.
Do not substitute tapioca flour for the cornstarch, as it will create a stretchy, "gloopy" texture rather than a creamy one.
If any lumps form despite whisking, simply use an immersion blender directly in the saucepan for a perfectly smooth result.
Store leftovers covered in the refrigerator for up to 3 days. The total time listed does not include chilling.