Preheat oven to 170°C and line a baking tray.
Melt the butter and golden syrup together in the microwave. Let stand for 1 minute, then stir in the bicarb soda until frothy.
In a bowl, whisk together the oats, flour, coconut, brown sugar and salt. Make a well, pour in the butter mixture and mix to form a dough. Add the boiling water and mix until combined.
Roll tablespoons of dough into balls, place on the tray and gently flatten. Bake for 12–14 minutes or until golden. Cool completely.
For the filling, microwave the chocolate, butter and cream for 1 minute. Stir, then continue microwaving in 30-second bursts until smooth (about 2½ minutes total tops!). Chill until thick and fudge-like (about 30 minutes in the freezer or 2 hours in the fridge).
Beat the chilled ganache with an electric mixer for about 30 seconds until light and fluffy. Sandwich between two cooled biscuits and enjoy!
