Heat the oven to 180°C regular bake and line the base and sides of a 20cm square tin with baking paper
Place the butter, sugar and golden syrup in a pot over a medium heat
Once the butter has melted, remove from the heat and mix in the rolled oats, flour, baking powder and spices
Add the remaining base ingredients and stir to combine
Firmly press into the prepared tin and bake for 18 minutes
Remove from the oven and set aside to cool to room temperature
Place the butter, cream cheese, icing sugar and orange zest in a large bowl and beat with an electric mixer until smooth and well combined
Spoon icing on top of base and spread out evenly, swirling if desired
Place in the fridge for at least 4 hours to allow the icing to set
Use a large sharp knife to cut into small pieces, cleaning the knife between cuts for clean icing lines
Keep in the fridge in an airtight container
