In a 16-ounce glass jar or airtight container, whisk together the rolled oats, protein powder, chia seeds, cocoa powder, and sea salt until no lumps remain.
Pour in the almond milk, vanilla extract, and maple syrup.
Stir the mixture vigorously for 30 seconds to ensure the protein powder is fully hydrated and chia seeds are distributed.
Drop the peanut butter into the center and use a knife to gently swirl it through the oats without fully incorporating it.
Seal the container and refrigerate for a minimum of 4 hours, or ideally overnight (8 hours), to allow the oats to soften and the mixture to thicken.
Before serving, stir the oats once and garnish with dark chocolate chips.