Add the rolled oats, cocoa powder, sweetener, vanilla, and a pinch of salt to a mason jar or lidded container.
Pour in the milk and stir very well until no dry cocoa pockets remain. (A small whisk helps if the cocoa clumps.)
Stir in about half of the peanut butter (or dollop it on top for a layered look).
Seal tightly and refrigerate for at least 4 hours, ideally overnight, until thick and creamy.
In the morning, stir again. If you want a looser texture, add a splash more milk. If desired, thin the remaining peanut butter with 1 tablespoon milk and drizzle over the top.
Top with raspberries (and chocolate chips if using) and serve cold, or warm in the microwave for 30–60 seconds.