Cook the apples with butter, cinnamon and maple syrup over medium heat for 4 to 5 minutes, until softened but not mushy. Let cool.
Mix the oats, milk, Greek yogurt, chia seeds, flaxseed, maple syrup, vanilla, cinnamon and salt. Divide between 4 jars and top with the cinnamon apples. Cover and refrigerate overnight.
Mix the crisp topping ingredients and toast in a skillet over medium-low heat until golden and fragrant. Cool completely and store separately.
Add the crisp topping right before eating so it stays crunchy.