Line a slice tray with baking paper.
Crush the biscuits into small pieces - you can use a food processor, or just bash them with the end of a rolling pin like I do (it's a great stress relief activity).
Melt the butter and chocolate together in microwave. I cook for 30 second spurts and mix together in between.
Add the melted butter & chocolate as well as the condensed milk to the crushed biscuits. Mix together to combine and then pour into the slice tray.
Using a metal spoon, spread slice evenly over the tray and push down to smooth.
Decorate with coconut if desired, and place in the fridge to set. Once set, slice into squares and enjoy!