Prepare chocolate sauce: pour water, balsamic vinegar into a saucepan. Then add sugar and half of the grated parmesan. Cook over medium heat until cheese is completely melted. Add chocolate and leave on fire until it melts. Pour in olive oil, mix. Remove the finished sauce from heat and cool.
In an oven preheated to 170 degrees, dry the slices of bread, cool. Put 1-2 teaspoons of chocolate sauce on the croutons, add the remaining parmesan flakes and arugula leaves.