This recipe has a neat little trick involving chocolate flavoured popped rice cereal; the kernels give an interesting crunch to the biscuits. Be careful when heating the chocolate, as it can burn easily.
For the biscuits
220g self-raising flour
1 tbsp bicarbonate of soda
80g caster sugar
100g 70% cocoa solids chocolate, finely chopped
2 tbsp cocoa powder
pinch of sea salt
150g unsalted butter, softened
100g golden syrup
For the filling
75g 70% cocoa solids chocolate, chopped
30g chocolate flavour popped rice cereal
1 quantity Salted butterscotch (see here; you won’t need it all but it keeps well in the fridge)
Preheat the oven to 140°C/fan 120°C/gas mark 1.
For the biscuits, combine the flour, bicarbonate of soda, sugar, chocolate, cocoa powder and salt in a large mixing bowl (or mix in a food mixer fitted with the beater attachment), then mix in the butter and golden syrup, beating until thoroughly combined.
Divide into 16 balls (about 1 heaped tbsp each), placing them evenly over 2 baking trays lined with baking parchment, then bake for 25–30 minutes. You may need to turn the tray around halfway through to ensure the biscuits cook evenly in the oven.
Place the baking tray on a cooling rack and leave to cool.
Meanwhile, make the filling. Melt the chocolate in a microwave on a low setting, stirring often, or place in a heatproof bowl and melt over a pan of simmering water (the bowl should not touch the water). Add the cereal and mix so the pieces are completely coated in chocolate.
Once the biscuits are cool, carefully remove them with a palette knife. Turn two of them upside-down and spread 1 tbsp of the chocolate filling on one biscuit and 1 tbsp of Salted butterscotch on another, then sandwich the 2 together. Repeat to sandwich all the biscuits.
Leave the biscuits for 30 minutes, to set the filling, before eating.