Heat the oven to 200C/180C fan/gas 4. Line two baking sheets with baking parchment and set aside.

Cream the butter with both sugars in a large mixing bowl using an electric whisk, then beat in the salt, egg and vanilla. Stir in the flour, bicarbonate of soda, chocolate and hazelnuts using a wooden spoon until well combined.

Scoop the dough onto the baking sheets in 24 heaps, well spaced apart. Bake for 10-12 mins or until lightly golden at the edges. Remove from the oven and allow to cool completely on the baking sheets. Spread 1 tsp of chocolate spread on the bottoms of half the cookies, then sandwich with the other halves. Will keep in a cake tin or airtight container for up to five days.