Grease & line an 18 cm (7") square baking tin (base measurement) with baking paper/parchment with sides overhanging (see notes).
Place chocolate (200g/7oz), salted butter (50g/2oz) & condensed milk (395g/14oz) into a medium sized glass bowl, and heat in microwave for 2 1/2 - 3 mins (in 30 second bursts, mixing between each) until melted & smooth.
Meanwhile, place biscuits (250g/9oz) in a food processor & process until fine crumbs (or place them in a sturdy plastic bag & bash them with something like a rolling pin).
Once chocolate has melted, add peanut butter (⅓ cup) & vanilla (¼ tsp), mixing to combine.
Then add biscuit crumbs, mixing well. Place mixture into prepared tin & smooth the top - I use a mini silicone spatula. Sprinkle coconut (1 tbsp) evenly over slice & refrigerate for 1½ hours or until set
Slice into 16 bars (or 24 bites - see notes) and serve