Line an 8×8-inch square pan with parchment, and spray with nonstick spray. Set aside.

Add dark chocolate to the top of a double boiler, or sit a large metal bowl over a stock pot of simmering water to create a bain-marie. Melt chocolate, stirring periodically, until completely melted.

Add butter and golden syrup and whisk gently to combine.

Remove from heat. Set aside and allow chocolate to cool for 25-30 minutes, or until very warm but not hot to the touch.

With a rubber spatula, fold in crushed Oreos and mini marshmallows. Stir until melted chocolate thoroughly coats all ingredients.

Pour into prepared tin. Use a rubber spatula to spread, pushing down gently to press the mixture into the tin.

Press extra Oreo pieces on top to decorate.

Cover pan with plastic wrap. Refrigerate 2 hours, or until chocolate sets.

Transfer slab to a cutting board. With a sharp chef’s knife, slice into squares and serve.

Store leftover rocky road in an airtight container in the refrigerator for up to 1 week.