Peel one of the bananas and place it in a bowl with the chia seeds. Mash together with a fork until they are well combined. You will end up with a mushy banana, chia seed paste.

Add vanilla extract and milk. Mix together until incorporated and lumps are gone.

Now we need to divide the chia seed mixture in half. Separate, then cover one and place it in the fridge.

To the other half, add the sweetener (if using) and cacao powder. Mix well. Cover and refrigerate overnight.

When ready to assemble the parfait, fill the bottom third with cacao chia, the second third with vanilla chia (place banana slices against glass), and then the cacao again. Add more banana slices and cacao nibs to the top.