Divide the rolled oats, chia seeds, brown sugar, and cinnamon equally between two mason jars or containers. I like to measure everything out beforehand so the actual assembly is quick and hassle-free. Stir the dry ingredients together in each jar to distribute the cinnamon and sugar evenly, which ensures consistent flavor in every spoonful.

In a liquid measuring cup or small bowl, whisk together the vegan protein powder and unsweetened non-dairy milk until smooth and fully combined. This prevents lumps of protein powder from settling and ensures an evenly distributed creamy texture throughout the oats. Divide this mixture equally between the two jars, pouring it over the dry ingredients.

Add half of the plain non-dairy yogurt and 1/4 teaspoon of vanilla extract to each jar. Stir everything together thoroughly until well combined—this is important so the protein powder and oats don't clump together overnight. If using banana, slice it and arrange it on top of the mixture. I find that keeping the banana on top rather than mixing it in prevents it from getting too soft and mushy by morning.

Seal the jars with lids and refrigerate for at least 4 hours, or preferably overnight (up to 24 hours). The oats will absorb the liquid and soften while the chia seeds will develop a pleasant gel-like texture that adds body to the mixture. Before eating, give the jar a gentle stir or shake, and add a splash more milk if you prefer a thinner consistency. Top with an extra pinch of cinnamon if desired.