Add milk, maple syrup, vanilla, sea salt, cacao or chocolate powder, and flax seeds to a high powdered blender. Blend on high until smooth and fully incorporated, 1-2 minutes. Alternatively, you can whisk all ingredients together in a large bowl, mixing in chia seeds last. This will have a different texture than the blended version, but works great as well.
Add chia seeds to a large airtight storage container and pour pudding mixture on top. Stir chia seeds into the pudding until incorporated. Then transfer to the refrigerator for at least 4 hours, or overnight. Shake the container or stir the pudding a couple of times to prevent lumping.
Arrange pudding in small individual containers such as mason jars, ramekins or drink glasses. Layer toppings between pudding or add them right on top. We like a little bit of everything.