Prepare the coffee and let it cool down.
Make the cream by mixing the whipping cream, cold water, and chocolate yogurt.
Melt the dark chocolate and milk chocolate with a small amount of milk and margarine to make the ganache.
Assemble the tart by layering the Macao biscuits and the coffee at the bottom, then topping with the cream mixture and the chocolate ganache.
Refrigerate the tart until ready to serve.
