Preparation
1. Lightly grease a 6-inch-by-2½-inch cake ring with the butter and place on a tray on a sheet of parchment paper.
2. Break each of the biscuits into almond size pieces by hand and set aside.
3. In a large bowl, combine the butter and sugar until the mixture starts to lighten.
4. Melt the 4 ounces of the dark chocolate and add to the butter mixture, stirring constantly.
5. Add the egg and beat to combine.
6. Fold in the biscuit pieces until they are all coated with the chocolate mixture.
7. Spoon the mixture into the prepared cake ring. Try to fill all of the gaps on the bottom of the ring because this will be the top when it is un-molded.
8. Chill the cake in the refrigerator for at least 3 hours.
9. Remove the cake from the refrigerator and let it stand.