Grate or finely dice the large apple directly into a medium bowl or container—I prefer grating because it distributes the apple flavor more evenly throughout the oats. Add the oats, chia seeds, cinnamon, and nutmeg to the bowl with the apple. Stir these dry ingredients together to combine evenly, ensuring the spices are well distributed throughout the oats.

Pour the milk into the bowl with the dry ingredient mixture from Step 1, then add the maple syrup and raisins. Stir everything together thoroughly, making sure all the oats are submerged and the mixture is well combined. The liquid should cover the oats slightly—if it seems too thick, add a splash more milk. This ensures the oats will soften and absorb the flavors evenly overnight.

Cover the bowl or container with a lid or plastic wrap and refrigerate for at least 6 hours, or preferably overnight. The overnight rest allows the oats to fully absorb the milk and soften while the cinnamon, apple, and raisins infuse the entire mixture with flavor. I find that letting it sit overnight creates the best texture and taste—the oats become creamy rather than crunchy.

Remove the overnight oat mixture from the refrigerator and give it a quick stir, adding a splash of milk if needed to reach your desired consistency. Transfer to a serving bowl or eat directly from the container. Top with a dollop of Greek yogurt, a handful of sliced or chopped almonds, and thin slices of fresh apple or additional grated apple for brightness and texture contrast.