Preheat the oven to 350°F (180°C). Line a baking sheet with parchment paper.
2. Step
In a large bowl, combine the eggs, vanilla cake mix, vegetable oil, and water. Beat with an electric hand mixer to combine.
3. Step
Pour the cake batter onto the prepared baking sheet and spread with a spatula into an even layer.
4. Step
Bake for 8 minutes, or until golden brown.
5. Step
Sift the cocoa powder through a fine-mesh sieve all over a clean kitchen towel.
6. Step
Flip the cake onto the cocoa powder-dusted towel and remove the parchment paper. Starting with a short end, roll up the cake with the towel.
7. Step
Refrigerate for 1 hour.
8. Step
In a medium bowl, whip the heavy cream and espresso powder with an electric hand mixer until fluffy.
9. Step
Add the mascarpone, sugar, and vanilla to the espresso cream and beat until smooth.
10. Step
Unroll the cake and spread with the espresso cream in an even layer, leaving 1½ inches (4 cm) from the top empty and reserving 1 cup (225 g) of espresso cream for decoration.
11. Step
Arrange the ladyfingers on the cake horizontally, 2 inches (5 cm) from the bottom. Brush the ladyfingers with the chilled espresso.
12. Step
Roll the cake back up, using the towel as a guide but not rolling it inside the cake.
13. Step
Refrigerate for another hour, then unwrap the cake.
14. Step
Transfer the remaining espresso cream to a piping bag.
15. Step
Pipe 6 espresso cream dollops on top of the tiramisu roll. Sprinkle chocolate shavings on top.
