Step 1

In a food processor, pulse biscuits and walnuts into a fine crumb. Add condensed milk and espresso, and pulse to combine. Roll mixture into balls and place on a tray lined with baking paper. Refrigerate to set.

Step 2

Melt chocolate in a small heatproof bowl in 30-second bursts in the microwave until smooth and liquid. Use two forks to dip and coat each ball in the chocolate. Shake off excess chocolate, then place on a tray lined with baking paper. Press a piece of walnut into the top. Repeat with remaining balls until all are coated and decorated.

Step 3

Allow chocolate to set. Store in an airtight container at room temperature or in the fridge.