Cake 

1. In a medium saucepan add your butter chunks and chocolate then place over low- medium heat and stir constantly until everything is melted together. Do not walk away you don't want the chocolate to burn, so cutting the butter into chunks and stirring continuously prevents this. 
2. Remove the pot from the heat and stir in the sugar and salt, once melted stir in the cream and golden syrup. 
3. Break the biscuits into small pieces, think postage stamp size, then gently fold them into the chocolate so everything is coated. 
4. Grease a 6-inch X 3-inch springform pan with butter then pour in all of the chocolate biscuit batter.  Use a spatula to gently pack it all into an even layer. Cover the pan with plastic wrap and chill in the fridge for four hours or overnight. 

Ganache

1. Warm the heavy cream, by microwave or stove. Add the chocolate pieces to a liquid measuring cup then, add the warm cream and golden syrup. Let sit for five minutes then, whisk to combine, it will take a minute but will then turn into a lush chocolate ganache. 
2. Gently remove the outer lining of the springform pan and if you want to use an angled spatula to release the cake from the bottom of the pan then use a large spatula to transfer the cake to a wire rack. Place a plate under the wire rack to catch the drippings of the chocolate. Gently pour the chocolate ganache over the cake and use an angled spatula to help cover the sides. Once the cake is covered use the remaining ganache to pour down the sides of the cake to create chocolate drips. Chill in the fridge for 20 minutes to set the ganache then transfer to a serving plate and enjoy. Store the cake in an air-tight container or covered with cling film/ plastic wrap in the fridge for up to one week.