1. Grind hazelnuts into a paste.
2. Combine with sifted flour, sugar and room temperature butter in a bowl. Mix and knead until a ball forms.
3. Flatten ball out, wrap with glad wrap and place in a fridge for at least 30mins.
4. Line a baking tray with baking paper.
5. Roll out dough to 1cm thick. Use a mould (I use a nozzle from my piping bag) and stamp out pieces. Weigh each piece out to ensure they are all 10-11 grams.
6. Roll into balls and place on the baking tray. Pat down the top of each ball with a damp finger.
7. Place balls into the fridge for 1 hour.
8. Preheat oven to 150°c.
9. Cook balls for 15 minutes.
8. Increase the temperature to 180°c and cook for a further 5 minutes. Baci must be light in colour and not golden brown.
9. Place on a cooling rack and let cool completely.
10. Load your piping bag with Nutella or melted dark chocolate. Pipe a dollop onto half of the Baci.
11. Place tops on Baci and serve!