01 - Line an 8x8 inch baking pan with parchment paper, ensuring some overhang for easy removal.
02 - Combine crushed biscuits, melted butter, and sugar in a bowl. Press firmly into the prepared pan creating an even layer. Chill in the refrigerator for 10 minutes.
03 - Place chopped chocolate and heavy cream in a heatproof bowl. Melt over simmering water or in 30-second microwave intervals, stirring until smooth. Stir in vanilla extract.
04 - Pour the melted chocolate mixture evenly over the chilled base and spread with a spatula.
05 - Sprinkle optional chopped nuts, mini chocolate chips, and sea salt over the chocolate layer.
06 - Refrigerate for at least 1 hour until the chocolate is firm.
07 - Lift bars from the pan using the parchment overhang and cut into 12 squares. Serve chilled or at room temperature.