Preheat the oven to 180 °C (350 °F) and line a baking sheet with parchment paper.

In a mixing bowl, cream together the softened butter and sugar until light and fluffy.

Add the eggs and vanilla extract to the bowl and mix well until combined.

In another bowl, sift together the flour and cocoa powder, then gradually add it to the butter mixture, stirring until well combined.

Fold in the chopped hazelnuts until evenly distributed throughout the dough.

Roll small balls of dough and place them on the prepared baking sheet, spaced apart.

Bake the cookies in the preheated oven for about 10-12 minutes, until firm but still soft in the middle.

While cookies are baking, melt the nougat until smooth.

After baking, make a small indentation in each cookie center and fill with melted nougat.

Dip each cookie into melted dark chocolate and allow the excess to drip off. Cool on a wire rack.