01 - Line an 8x8 inch baking pan with parchment paper, leaving an overhang for easy removal.
02 - Combine crushed biscuits, melted butter, and sugar in a bowl and press firmly into the bottom of the prepared pan. Chill in the refrigerator for 10 minutes.
03 - Place chopped chocolate and heavy cream in a heatproof bowl and melt over simmering water or in 30-second microwave intervals, stirring until smooth. Stir in vanilla extract.
04 - Pour melted chocolate mixture evenly over the chilled biscuit base using a spatula.
05 - Optionally sprinkle chopped nuts, mini chocolate chips, and a pinch of sea salt over the chocolate layer.
06 - Refrigerate for at least 1 hour until the layers are firm.
07 - Lift the bars from the pan using the parchment overhang and cut into 12 pieces. Serve chilled or at room temperature.