This dense, ultra-rich dessert, enriched with crushed tea biscuits and glazed with chocolate ganache, was inspired by the cake Prince William has chosen as the groom’s cake for his royal wedding.
For the cake: Lightly coat a 9-inch springform pan with nonstick spray.
Line bottom of pan with parchment paper round.
Stir butter and chocolate in a large saucepan over low heat until melted and smooth.
Stir in cream and golden syrup.
Remove from heat; mix in chopped biscuit pieces to evenly incorporate.
Pour chocolate mixture into prepared pan; smooth top.
Cover and refrigerate until set, at least 3 hours or overnight.
For the glaze: Place chocolate in a medium bowl.
Bring cream and corn syrup to a simmer in a small saucepan over medium heat.
Pour over chocolate.
Let stand 5 minutes, then stir until melted and smooth.
Let cool slightly, stirring occasionally, until glaze is slightly thickened but still pourable.
Wrap a warm, damp kitchen towel around cake pan.
Remove pan sides.
Invert cake onto a cardboard round or the removable bottom from a 9-inch tart pan.
Remove cake pan bottom and peel off parchment paper.
Place cake on a wire rack set over a rimmed baking sheet.
Pour glaze over cake, allowing it to drip down sides; spread as needed to cover cake.
Refrigerate cake until glaze sets, about 30 minutes.
Note: Can be made 1 day ahead.
Cover with cake dome and keep chilled.
Cut into wedges and serve.