01 - In a medium bowl, combine rolled oats, milk, Greek yogurt, chia seeds, maple syrup, ground cinnamon, and vanilla extract. Stir thoroughly until evenly blended.
02 - In a small bowl, toss the diced apple with fresh lemon juice, ground cinnamon, and maple syrup until the apple pieces are well coated.
03 - In a separate bowl, combine rolled oats, chopped nuts, melted butter, brown sugar, and cinnamon. Mix until the mixture forms coarse, crumbly clusters.
04 - Divide the oat base evenly between two jars or containers. Spoon the apple layer on top of each, then sprinkle generously with the crumble topping.
05 - Seal the jars or containers tightly and refrigerate for at least 6 to 8 hours to allow the oats to absorb the liquid and soften.
06 - Enjoy cold straight from the fridge or let sit briefly at room temperature. For a warmer option, microwave for 30 to 60 seconds.