Prepare Oreos: Take 2-3 Oreo cookies. Crush one of them into fine crumbs (you can use a bag and rolling pin or a food processor). Break the other 1-2 Oreos into larger chunks. This gives a nice mix of flavor and texture.
Combine Base Ingredients: In a jar or airtight container, combine the rolled oats, milk, Greek yogurt (if using), chia seeds, sweetener, vanilla extract, and a pinch of salt. If you want a more intense chocolate flavor in the oats themselves, add ½ to 1 tablespoon of unsweetened cocoa powder.
Add Oreo Crumbs: Add the finely crushed Oreo crumbs to the oat mixture. Stir very well to ensure all ingredients are thoroughly combined and the Oreo crumbs are integrated, giving the oats a chocolatey flavor and color.
Add Oreo Chunks: Gently fold in the larger Oreo chunks. Try not to overmix at this stage if you want distinct cookie pieces in the morning.
Chill: Cover the jar/container and refrigerate for at least 4 hours, or ideally overnight (8+ hours). This allows the oats to soften and the chia seeds to swell, creating a thick and creamy consistency.
Serve and Top: The next morning, give the oats a gentle stir. If the consistency is too thick, add a splash more milk until desired.
Optional Toppings: Top with additional crumbled Oreo cookies, a drizzle of chocolate syrup, a dollop of whipped cream or extra Greek yogurt, or a sprinkle of mini chocolate chips before serving.