1. 1. Prepare the oat base: In a medium jar or container, combine rolled oats, chia seeds, milk, Greek yogurt, 1 tablespoon sweetener, and 1/4 teaspoon vanilla extract. Stir well until combined. 2. Create the berry layer: In a small bowl, mash about half of the mixed berries with a fork. Add a tiny splash of milk and 1 teaspoon sweetener if desired. 3. Prepare the cheesecake swirl: In another small bowl, mix softened cream cheese with remaining 1 tablespoon sweetener and 1/4 teaspoon vanilla extract until smooth. Add a tiny splash of milk if too stiff. 4. Layer: Spoon half of the oat mixture into your serving jar(s). Dollop half of the mashed berries and half of the cream cheese mixture on top. Gently swirl with a knife. 5. Repeat layers: Add remaining oat mixture, then remaining mashed berries and cream cheese. Swirl again. Top with a few whole berries. 6. Chill: Cover and refrigerate for at least 6 hours or overnight (8-12 hours). 7. Serve: In the morning, stir, add desired toppings (fresh berries, granola, extra maple syrup), and enjoy cold.