01 -
Combine the spice cake mix, quick-cooking oats, and melted unsalted butter in a bowl. Mix thoroughly until crumbly.
02 -
Spread the canned apple pie filling evenly over the bottom of a 5–6 litre slow cooker.
03 -
Distribute the cake mixture evenly over the apple layer.
04 -
Sprinkle the chopped walnuts over the top, if using.
05 -
Cover and cook on HIGH setting for 2 hours.
06 -
Serve warm or chilled, optionally accompanied by ice cream or whipped cream.