Whisk together the 2 cups hot water and 5 teaspoons espresso powder in a shallow dish. I like to use a pie plate.
In the bowl of a stand mixer, beat together the 2 cups mascarpone cheese and ½ cup powdered sugar using the paddle attachment until creamy. Scrape the sides of the bowl with a spatula.
Switch to the whisk attachment. Add the 2 teaspoons vanilla extract. Turn the mixer on low speed. Slowly pour the 1 ½ cups heavy whipping cream into the cheese mixture. As the mixture thickens, gradually increase the speed of the mixer and continue whisking until the cream has been whipped to stiff peaks.
The mixture will have a glossy sheen. Stiff peaks mean when you invert the whisk the cream will form and hold a stiff peak that does not fold over. Do not overwhip the cream. Doing so will cause the cream to split and turn into butter.
Dip the 1 7oz package ladyfingers into the now-cooled espresso for no more than 2 seconds on each side.
Use the soaked cookies to line the bottom of the baking dish. You may need to break a few of the ladyfingers to fill in any gaps.
Top the ladyfingers with one-third of the mascarpone mixture. Use an offset spatula to smooth the layer of cream.
Dip more ladyfingers in the espresso and layer them on top of the mascarpone mixture.
Top with half of the remaining mascarpone cream mixture. Use an offset spatula to smooth the layer of cream.
Dip more ladyfingers in the espresso and layer them on top of the mascarpone mixture.
Top with the remaining mascarpone mixture.
For the best results, cover with plastic wrap and refrigerate the tiramisu for at least 4 hours. Overnight is preferable.
Before serving top the tiramisu with a generous dusting of cocoa powder. To make it extra special you could also add chocolate shavings.