Beat eggs (no need to separate them) with sugar until it’s three times in volume. Sift flour together with cacao. Using a spatula, fold in flour by thirds; be very gentle with dough, so you don't over mix it and lose the fluffiness. Place dough into 9 inch pan. Bake at 350F for 30 minutes, check it with a wooden toothpick. If the cake is ready, dough should not stick to the toothpick.
Once the cake cools, cut the cake into three or four slices.
Soak the slices with whipping cream and liqueur combined together; set it aside.
Melt chocolate chips in a microwave, stir chocolate every few seconds not to overcook. Whip together chocolate, butter and condensed milk. Whip until well combined.
In a separate bowl, whisk very cold heavy whipping cream until soft peaks. Fold in chocolate butter mixture into whipped cream.
Place a layer of cake on a plate, cover with cream, repeat until you ran out of cake layers.
Using the remaining cream, decorate the outside of the cake.
Dust sides of the cake with cacao powder and some shredded chocolate or decorate as you wish.