Place a sheet of parchment paper over a baking sheet. Set aside.

In a dry non-stick pan over medium heat pour in the sugar.

Mix constantly with a silicone spatula until it becomes light caramel colored. Do not let it get dark brown - that is burnt sugar! Discard and start again if it gets too dark.

Turn off the heat and add in the butter and hazelnuts.

Mix vigorously.

Pour onto the parchment paper and spread around so that there is a thin layer of caramel and hazelnuts.

Allow to cool for at least one hour on the counter.

Using the bottom of your sauce pan, hit the brittle to break it up into little pieces - don't go overboard - you don't want hazelnut brittle dust. Just a few swift taps will do. Careful not to eat it all before you decorate the cake - it is that good!