Start by crushing the digestive biscuits or graham crackers into fine crumbs. Combine the crumbs with melted unsalted butter until well mixed, then press into the bottom of a 9-inch springform pan. Refrigerate for 30 minutes.

In a saucepan, combine sweetened condensed milk, unsalted butter, brown sugar, and golden syrup. Heat over medium-low heat for 8-10 minutes, stirring constantly until thickened. Pour over the chilled biscuit base and refrigerate for at least 1 hour to set.

Beat softened full-fat cream cheese until smooth. Gradually add powdered sugar and vanilla extract while mixing. Whip heavy cream to stiff peaks, then fold into the cream cheese mixture until fully incorporated.

Spread the cheesecake filling evenly over the caramel layer in the springform pan. Cover and refrigerate for at least 4 hours, preferably overnight.

Melt dark or milk chocolate with heavy cream until smooth. Pour over the cheesecake layer for an even coating and chill for 1-2 hours until set.

Once chilled, remove the cheesecake from the springform pan. Dust with optional sea salt and slice with a warm knife for clean edges before serving.