Combine water and sugar in a small pan over medium high heat, swirling until sugar dissolves. Continue swirling until sugar begins to turn a medium golden color.
Add hazelnuts and stir with a spoon until they are completely coated.
Pour nuts onto a baking sheet lined with a silpat or parchment paper.
Working quickly with two forks, separate enough nuts to decorate the top of the tiramisu.
When remaining nuts are cool, pulse them in a food processor a few times to break up large pieces. They should look like this.