Preheat the oven to 350°f / 180°c. Grease a 9”x13” (23x33cm) baking tin and line with a piece of parchment paper that overhangs the two long sides of the tin, securing in place with metal clips.

Combine the flour, oats, coconut and salt in a large bowl. Place the butter, golden syrup or honey and brown sugar in a saucepan and cook over a medium heat, stirring every now and then, until melted. remove from the heat and add the water and the baking soda, and stir together for a minute until the mixture is a little foamy. Pour this over the oat mixture and mix together until well combined.

While the Anzac mixture is still warm, tip it into the prepared tin and press it into a flat even layer - I like using an offset spatula to spread it out then use a greased metal ⅓ cup measure to flatten.

Bake for 20 to 25 minutes, or until golden brown and a little darker around the edges. Leave to cool in the tin while you make the caramel.

Add all the caramel filling ingredients to a medium sized saucepan and cook, stirring constantly, until the mixture comes to a simmer. reduce the heat to low and continue to stir, scraping the bottom of the pan regularly to prevent catching, for 10-15 minutes, or until the mixture has thickened and darkened a shade or two, and reads 235°f /112°c on a candy thermometer.

Remove from the heat and pour the caramel over the base. This mixture is very hot, so ease it into the corners by lifting and tilting the tin as needed. Set aside to cool for 30 minutes.

Pour the melted chocolate over the caramel and use an offset spatula to spread it out evenly. Pop the tin in the refrigerator and leave for a couple of hours to allow everything to fully set. If you want to sprinkle with sea salt, wait until the chocolate is slightly tacky before sprinkling otherwise it will dissolve.

To serve, remove from the tin using the parchment paper and cut into squares with a sharp knife. Store in an airtight container in the fridge, and come to room temperature before serving.