Crumble the cookies and put half of it in a small but wide glass.
Mix the yoghurt with the roasted hazelnuts and vanilla. You can add some honey, maple syrup, if you have a sweet tooth, or a spoonful of dry Sherry or almond liquor. Pour half of this over the cookies.
Scatter the second half of the crumble over the yogurt, then cover with the remaining yoghurt.
Scatter some chopped roasted hazelnuts on top, then chill until serving.
Drizzle some honey or maple syrup on top, just before serving (optional).