8 ounces plain tea biscuits (we suggest either digestive or rich tea bisuits), broken into rough almond-sized pieces
Lightly grease a 6-inch springform pan (or cake ring). Line the bottom with parchment (if using a springform pan), grease the parchment. Set aside.
Cream together the butter and sugar until lighter in color and fully incorporated.
Place chocolate chips in a glass bowl and heat in the microwave on 30 second bursts, stirring between cooking, until almost melted. Stir until smooth. Add chocolate to creamed butter and sugar mixture and stir. Add egg and continue to stir until completely mixed in.
Fold in the biscuits pieces and stir gently until all pieces are completed coated in the chocolate mixture. Using the back of a spoon, press mixture into prepared pan, taking care to spead evenly to cover any gaps.
Chill the cake in the fridge for at least 2 hours. When ready to remove the cake from the frdige, melt the dark chocolate. Remove chilled cake and unmold onto a wire rack. Spoon the melted chocolate all over the cake and smooth the top and sides using an offset spatula.
Allow the chocolate to set at room temperature. Slice & serve.