Preheat oven to 180 C/160 C fan and line a baking tray.
Freshly grind the hazelnuts in a nut grinder, or process them in a high powered blender until they are finely chopped.
Cream the butter and sugar together until light and fluffy and white in colour.
Add the ground hazelnuts and flour, and combine well.
Shape into small balls about the size of a small walnut, flatten slightly and place on the baking tray.
Press a whole hazelnut into the top of each cookie.
Bake for 15-20 minutes.
Leave on the baking tray to cool completely before storing in an airtight container. Cookies will keep well for several days.
Notes
Bestemor recommends baking one biscuit on its own to judge the cooking time needed for your particular oven, as all ovens are different.To measure 1 dl, use a measuring jug marked in millilitres and pour enough sugar in the jug until it reaches 100 ml.