01 - In a medium bowl, combine rolled oats, milk, Greek yogurt, chia seeds, maple syrup, ground cinnamon, and vanilla extract. Stir thoroughly until all ingredients are evenly incorporated and the mixture is smooth.
02 - In a small bowl, toss the diced apple with lemon juice, cinnamon, and maple syrup until the apple pieces are well coated and fragrant.
03 - In a separate bowl, mix rolled oats, chopped nuts, melted butter, brown sugar, and cinnamon together until the mixture resembles a coarse, crumbly texture.
04 - Divide the oat base mixture evenly between two jars or airtight containers. Layer the seasoned apple pieces on top of the oats in each jar, then sprinkle the crumble topping generously over the apple layer.
05 - Seal the jars or containers with lids and refrigerate for at least 6 to 8 hours, allowing the oats to absorb the liquid and soften into a creamy consistency.
06 - Enjoy straight from the refrigerator cold or let sit briefly at room temperature. For a warm and cozy option, heat in the microwave for 30 to 45 seconds before serving.