In a small saucepot on low heat, warm 1/2 cup of heavy cream. Once the cream is warm, turn off heat and stir in the chocolate. Continue to stir until completely melted.
In the bowl of a stand mixer or with an electric mixer, Beat the remaining cup of heavy cream into whipped cream until soft peaks form. Set aside 1/3 cup for the topping at the end. Keep refrigerated.
With the remaining whipped cream, gently fold in the melted chocolate until just combined. Reserve a small amount of chocolate for the cups.
Divide the chocolate mousse into bowls, filling halfway. Spoon 1 tsp of cookie butter and a touch of melted chocolate in the centre. Cover with more mousse and chill for at least 1 hour.
To serve: dollop 1 tsp of reserved whipped topping, drizzle melted cookie butter overtop and finish with cookie crumbs and chocolate shavings. Enjoy!