Preheat oven to 160 degrees celsius (fan forced). Grease and line a 20cmX20cm square cake tin with baking paper and set aside.
Place the Weet-Bix into the Thermomix bowl and crush on Speed 8, 10 seconds.
Add the cocoa powder, brown sugar, melted butter, coconut and egg and mix on Speed 4, 5 seconds. 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 on Speed 3, 60 degrees, 3 minutes (or until completely melted. Pour over the top of the slice.
Working quickly, place the chocolate Freckles in lines.
Allow to set in the fridge for 2 hours before slicing.