Preheat oven to 160 degrees celsius (fan-forced) and line an 18 x 28cm slice tray with baking paper.
Place the Weet-Bix into the Thermomix bowl and mix for 10 seconds, Speed 7 until finely crushed. Transfer the Weet-Bix crumbs to a seperate bowl and set aside until needed.
Without washing the bowl, place the butter into the Thermomix bowl and melt for 3 minutes, 60 degrees, Speed 2.
Add the crushed Weet-Bix, cocoa powder, brown sugar, coconut and egg and mix for 10 seconds, Speed 4. Scrape down the sides of the bowl and mix for a further 10 seconds, Speed 4.
Transfer the mixture to your prepared slice tray and cook for 18 - 20 minutes, or until the slice is firm to the touch.
Allow the slice to cool completely in the tin before preparing the icing. Place all of the icing ingredients into a clean and dry Thermomix bowl and mix for 30 seconds, Speed 3. Scrape down the sides of the bowl and mix for a further 20 seconds, Speed 3 or until smooth.
Pour the icing over the completely cooled slice and use a butter knife to smooth. Decorate with 100s and 1000s or sprinkles.
Notes
RECIPE NOTES & TIPS
It's completely fine for there to be a little melted butter remaining on top of the slice when it comes out of the oven. It will disappear very quickly.
When you are making this recipe, it's important to make sure you allow the slice to cool completely before adding the icing, otherwise it will be impossible to spread.
Place the slice into the fridge or freezer to hurry up the cooling process before adding the icing.
Store in an airtight container and store in the fridge for up to 1 week.
This slice can be frozen in an airtight container for up to 3 months.