In a medium bowl, mix together rolled oats, Greek yogurt, and milk until well combined.

Stir in chia seeds and any optional sweetener, mixing until evenly distributed.

Transfer the mixture into an airtight container or individual jars, and refrigerate for at least 4 hours.

The next morning, stir the oats and add a splash of milk if they're too thick.

Top with freshly sliced strawberries and gently fold them in if desired.

Sprinkle granola on top, and add nuts or seeds for extra texture.

Serve in bowls or directly from the jars.