Mix the hazelnuts, the flour and sugar in a bowl. Cut the cold butter in pieces into it and mix it together with your hands or your (kitchen-aid) food processor. Add the water step by step and stop when you get a smooth dough.
Now let the dough covered in plastic wrap rest in the fridge for at least an 1 hour until you roll it out.
While the dough is resting, wash the apricots and cut them into slices.
Preheat the oven to 200 degrees Celcius (Ober-/Unterhitze).
Cut the dough into 3 pieces, so that you get later 3 mini galette. If you want one big one, than leave the dough in one piece.
Roll out one of the pieces on an flour-covered surface into a round shape.
Place it now on a baking sheet and add in the middle some apricot jam and 1/3 of the apricots slices.
Now fold the sides of the dough over the filling as far as possible. Then you'll have a beautiful galette.
Repeat step 5-8 for the other two mini galettes.
Now bake one at a time for 15-20 minutes. Until the dough turns golden brown.
Let it cool down a little bit and then serve it with a scoop of vanilla ice cream.