Place 70% chocolate and butter in a bowl and set over a saucepan of simmering water. Stir to melt and combine. Remove from heat and set aside to cool until needed.
Combine remaining ingredients in the bowl of an electric mixer fitted with a paddle attachment and beat until light and fluffy. Add cooled chocolate butter mixture and mix until well combined
Spoon tablespoons of mixture onto baking trays lined with baking paper. Dot the top of the cookies with the dark chocolate chips, pressing gently into the dough. Bake for 12-13 minutes in the preheated oven. Remove from oven and set aside to cool.
Meanwhile, to make the Chantilly Cream, combine cream and sugar in bowl of electric mixer fitted with the whisk attachment and whisk until soft peaks form.
Stir the Frangelico through the cream mixture.
Serve Brookies topped with a little extra grated chocolate and a dollop of Chantilly Cream.