In a bowl combine all the ingredients for the pastry and quickly knead till smooth. Please in a container with a lid and refrigerate for 30 to 60 minutes. The pastry needs to be firm enough to be rolled out.
Grease a 24cm tart or pie tin. Roll out the pastry on a floured work surface and fit into the tin. Shape an edge and prick the pastry several times with a fork. Place in the refrigerator for a further 30 minutes.
Preheat your oven to 180 C / Gas 4. Cover the pastry with greaseproof paper and cover with dry beans or pastry weights. Bake in the preheated oven for 20 minutes. Remove from the oven and let cool completely.
In the meantime roast hazelnuts in an ungreased frying pan, then chop coarsely.
In a bowl beat butter. sugar, vanilla sugar and cream till smooth. Add egg and beat again till smooth. Spread on the pastry.
Peel, core and slice pears. Arrange in an overlapping pattern and scatter hazelnuts on top.