01 -
Heat your oven to 175°C (350°F). Line a 20 x 20cm (8 x 8 inch) baking dish with non-stick baking paper, leaving an overhang on the sides to help you easily lift the bars out later.
02 -
In a medium bowl, combine the flour, rolled oats, salt, and baking soda, mixing well. In a separate bowl, mix together the melted butter, vanilla, and brown sugar. Pour the wet ingredients into the dry ingredients and stir until everything is thoroughly combined.
03 -
Take about three-quarters of the oatmeal mixture (reserve about 150g/5.2oz for the topping) and press it firmly into the lined baking dish, creating an even layer. Bake for 12 minutes until lightly golden. Remove from the oven and let cool for 15 minutes.
04 -
While the base is baking, prepare the cheesecake filling. In a bowl, combine the room temperature cream cheese, brown sugar, lemon zest, and egg. Beat until smooth and creamy. Set aside.
05 -
In another bowl, mix together the chopped apples, brown sugar, cornstarch, and cinnamon until the apples are evenly coated. Set aside.
06 -
Once the base has cooled for 15 minutes, spread the cheesecake mixture evenly over it. Next, distribute the apple mixture evenly on top of the cheesecake layer. Finally, crumble the reserved oatmeal mixture between your fingers and sprinkle it over the apple layer.
07 -
Return the dish to the oven and bake for an additional 22-25 minutes, until the crumble topping is light golden brown and cooked through.
08 -
Remove the bars from the oven and let them cool on the counter for 30 minutes. Then refrigerate for at least another 30 minutes or until completely cool. This chilling step is crucial - cutting the bars while they're still warm will cause them to fall apart.
09 -
Once fully chilled, use the parchment paper overhang to lift the entire dessert out of the baking dish. Place on a cutting board and slice into 9 even squares. Serve and enjoy!