Coffee Petit Beurre Cake

Directions
Brew a strong coffee and let it cool to room temperature.
In a large bowl, whip the heavy cream with the powdered sugar until stiff. Add the mascarpone and vanilla extract, then mix until smooth and homogeneous.
Quickly dip the Petit Beurre biscuits in the cooled coffee, one by one, and arrange a first layer of biscuits in the bottom of a rectangular dish.
Spread a layer of mascarpone cream on the biscuits, then add a second layer of biscuits soaked in coffee. Repeat until all the ingredients are used up, finishing with a layer of cream.
Dust the top of the cake with cocoa powder.
Refrigerate the cake for at least 4 hours, or ideally overnight, before serving.