Start by preheating the oven to 175℃/345℉. Line a 23cmx33cm baking tin with baking paper, over lapping 2 of the 4 sides (making for an easier release once baked). Give it a quick spray with Cook & Spray just to be sure. Set aside.
In a large bowl, add the softened butter, sugar, eggs, golden syrup, and vanilla essence. Whisk using an electric handheld whisk or stand mixer. Mix until mostly combined, about 2-3 minutes.
In a separate medium bowl, add the coconut milk and milk together. Microwave for 90 seconds or until hot. Add the cocoa powder to the warm liquid and whisk until well combined. Allow to slightly cool before adding it to the butter mixture. Once added, whisk until well combined, about 1 minute.
Add the flour, baking powder, salt and desiccated coconut to the wet ingredients and whisk until there are no flour pockets left, about 1-2 minutes. Do not overmix.
Pour the batter into the prepared baking tin and spread evenly. Bake for 45-50 minutes or until you poke the sponge with a skewer or toothpick and it comes out clean.
Once the sponge has mostly cooled, you can start sectioning the sponge into rusks using a serrated knife. Note: Aim for 4 rusks lengthwise and 7 rusks width wise (this is a personal preference but you can slice them thicker or thinner - it's up to you). The thicker they are the longer they will take to dry.
Drying: Preheat the oven to 100℃/212℉. Lay the sectioned sponge out onto a baking tray that's been lined with a rack, ensuring the tray isn't overcrowded. Place in the oven, with the door slightly ajar (using a cloth) ,and dry for 6 hours or until fully dried (overnight can also be an option). Note: the rusks must be fully dried otherwise they'll slowly start to soften and stale.
Once the rusks have fully dried, cut the chocolate into smaller pieces and add to a deep saucer. Place in the microwave for 1-2 minutes until fully melted. Generously dip the top of the rusk in the melted chocolate and place back onto the drying rack. Allow the chocolate to fully cool and harden. Note: depending on how cold it is, either leave it on the counter top to harden or in the fridge for 30 minutes or until fully hardened.
Once hardened, it's time to make that hot cup of coffee and get dunking!
