Cake Preparation:
Preheat the oven to 180°C (350°F). Grease and line two 9-inch cake pans.
Make the batter: In a large bowl, whisk together flour, cocoa, sugar, baking soda, baking powder, and salt. In another bowl, mix oil, eggs, vanilla, cream, and coffee. Combine the wet and dry ingredients until smooth.
Bake the cake: Divide the batter between the prepared pans. Bake for 35-40 minutes, or until a toothpick inserted comes out clean. Let cool, then remove from pans.
Vanilla Cream Filling:
Prepare the cream: In a saucepan, whisk flour and milk over medium heat until thick (like béchamel). Cool slightly, add vanilla. Cream the butter and powdered sugar until light, then gradually blend in the milk mixture until smooth.
Cut and fill: Slice each cake horizontally to create four layers. Spread vanilla cream between the first and second layers.
Chocolate Mousse:
Make mousse: Fold melted chocolate into whipped cream until uniform. Spread over the second layer of cake, then top with crushed cookies.
Chocolate Ganache:
Prepare ganache: Heat cream until just simmering, then pour over chopped milk chocolate. Stir until smooth.
Assemble: Place the third cake layer on top of the mousse, add more cookie crumbs, then the last cake layer. Pour ganache over the top, allowing it to drip down the sides.
Decoration:
Decorate: Once ganache is set, pipe additional mousse on top and decorate with chocolate shavings and pieces.
Chill: Refrigerate the cake until ready to serve.
