1. Start with the nutella filling. Prepare a wooden board or similar with baking parchment or some plastic wrap. Use a spoon and place 16-18 portions of Nutella on the prepared board, a heaping teaspoon each. Place it in the freezer and let it freeze for about one hour. The Nutella has to get harder, but not completely frozen.

2. Preheat the oven to 180°C (350°F). Prepare two baking sheets with baking parchment and set them aside. Chop the chocolate and set it aside. Combine flour, baking soda and salt in a bowl and set aside.

3. In a large bowl mix butter and sugars and beat on high speed until light and fluffy. Add the egg and vanilla extract and beat on high speed until well combined. Add the flour mixture gradually and mix until just combined. Fold in the chopped chocolate.

4. Take the Nutella out of the freezer. Take a small portion of the dough and press one of the frozen Nutella pieces into the dough and cover it completely with dough. Shape each dough portion into a ball, flatten it lightly and place them on the baking sheet. Bake the cookies for about 14-16 minutes or until the edges start to brown. Take the cookies out of the oven and let them cool down on the baking sheet for a couple of minutes, then let them cool down completely on a wire rack. Store in an airtight container.