- In a microwave-safe bowl, microwave chopped chocolate until almost melted, stirring after each minute. Set aside to cool slightly.
- Beat eggs and caster sugar with electric beater for five minutes.
- Stir in cooled chocolate.
- Fold in 3/4 cup whipped cream.
- Refrigerate until needed.
Set aside 1/4 cup crushed malt balls.
Fold together mascarpone, 7 ounces whipped cream, and remaining malt balls. Remove the base of an 8-inch spring form pan and place the ring on a large serving plate (ring will serve as a mold for the cake). Cut a strip of parchment paper and line side of ring. Dip cookies, one at a time, into liqueur and place in single layer in mold to cover base. Spread half mascarpone mixture over cookies. Top with another layer of cookies dipped in liqueur.
Spread chocolate mousse over cookies. Top with one more layer of cookies dipped in liqueur. Spread remaining mascarpone mixture over cookies and sprinkle with the 1/4 cup reserved malt balls.
Cover and refrigerate overnight. Then remove spring form, peel away parchment paper, cut, and serve.