Preheat the oven to 150°C. Grease and line a 3cm deep, 16cm x 28cm (base) baking pan with baking paper.
Mix together the dry ingredients:
Sift the flour, baking soda and spices into a large bowl. Add the oats, apple and sultanas and stir to combine.
Mix together the wet ingredients:
In a seperate bowl, whisk together the yoghurt, egg, apple juice and honey. Add to the flour mixture and using a metal spoon, fold until just combined. Do not over-mix.
Cooking the bars:
Spoon this mixture into the prepared baking tray and sprinkle with walnuts. Bake in a preheated oven for 40 - 45 minutes, or until a skewer inserted into the centre comes clean. Remove from the oven and allow the apple oat bars to cool completely before cutting into 18 pieces.
This also works with maple syrup instead of honey. Top with flaked almonds, instead of walnuts.
Store in an airtight container. The apple oat bars can also be frozen.