Preheat oven to 180*C
In a saucepan melt the butter until it goes brown. It goes from light brown to brown pretty steadily so keep watch! Make sure it does not burn..you will be able to smell the difference.
Once the butter is browned add in the sugar, egg and mix till smooth.
Mix in the ground hazelnuts, oat flour, baking soda and salt.
Chop chocolate into chunks and fold in.
At this point you can let the dough rest it in the fridge overnight EPIC results. But you can also just cool the dough in the fridge for 30 mins to prevent the dough for spreaing too much.
Bake for 7/8 mins for SOFT CHEWY cookies. The longer you leave the the chewier they get. They are typically beautifuly soft straight out of the oven. The next day they are even better.