Step 1

Grease a 20cm (base) springform pan. Line base and side with baking paper. Place biscuits in a food processor. Process until mixture resembles fine breadcrumbs. Add butter. Process until combined. Press mixture over base of pan. Refrigerate for 30 minutes.

Step 2

Meanwhile, place chocolate in a large heatproof bowl over a saucepan of simmering water. Stir with a metal spoon for 10 minutes or until melted and smooth. Remove from heat. Cool for 10 minutes (see note).

Step 3

Using an electric mixer, beat cream and liqueur until soft peaks form. Fold cream mixture into chocolate. Pour chocolate mixture over base in prepared pan. Smooth with a spatula. Cover. Refrigerate for 3 hours or until set. Dust with cocoa. Serve.