Whisk the eggs, milk, sparkling water, salt, vegetable oil, cocoa powder, and vanilla sugar in a mixing bowl.

Whisk in the wheat flour until combined, then pass the batter through a fine sieve to remove lumps.

Cook a thin pancake in a lightly oiled pan over medium heat, then turn it when the underside is set.

Repeat until four pancakes are cooked, then let the pancakes cool completely on a plate.

Beat the mascarpone cheese, whipping cream, and powdered sugar until the filling is thick and smooth.

Arrange the four pancakes in an overlapping row, then spread the mascarpone filling along their center.

Crush the Oreo cookies, then sprinkle them over the filling.

Fold in the pancake edges, then roll the pancakes tightly into one long roll.

Refrigerate the pancake roll overnight until firm, then slice it into four portions.

Dust the slices with unsweetened cocoa powder before serving.