Step 1

Line a deep 19cm (8-inch) square cake pan with aluminium foil; grease top of foil.

Step 2

Combine marshmallows, butter and the water in a medium saucepan over medium heat; cook, stirring, until marshmallows are melted. (Mixture will be bubbling gently while the marshmallows are dissolving).

Step 3

Remove from heat, stir in chocolate and extract. Stir with a wooden spoon until chocolate is melted.

Step 4

Stir in nuts; beat with a wooden spoon until mixture becomes sticky. Pour mixture into pan. Refrigerate for 4 hours or overnight before cutting into bars.