In a bowl, bash the bourbon biscuits until they resemble breadcrumbs. Pour in the melted butter and stir to combine.

Push the biscuits into the base of your tart tin, smoothing out the top. Put in the fridge.

In a bowl, whisk your whipping cream with an electric whisk, until soft yet firm. This should take about 5 minutes.

In another bowl, melt 2 bars of the chocolate. Fold the cream into the chocolate, being careful not to disturb the air bubbles.

Pour the mousse mixture on top of your biscuit base, leave in the fridge to set for 10-15 minutes.

Melt your final bar of chocolate and pour over the mousse mixture. Leave in the fridge to set for 45-60 minutes.

Remove from your tart tin, slice and serve.