Preheat oven to 160 degrees celsius (fan forced).
Grease and line a 20cm x 20cm square cake tin with baking paper and set aside.
Place the Weet-Bix into the Thermomix bowl and crush for 10 seconds, Speed 8.
Add the cocoa powder, brown sugar, melted butter, coconut and egg and mix for 5 seconds, Speed 4. Scrape down the sides of the bowl and repeat for a further 5 seconds.
Press mixture firmly into the prepared cake tin.
Bake for 15 to 20 minutes or until firm to the touch. Allow to cool.
Melt the chocolate and coconut oil (optional) in a clean Thermomix bowl for 3 minutes, 60 degrees, Speed 3, (or until completely melted. Spread over the top of the slice.
Working quickly, place the chocolate Freckles in lines.
Allow to set in the fridge for 2 hours, then remove from fridge for 30 minutes before slicing.