To remove brown paper skin of hazelnuts, first toast them in a 400° oven for 5 to 6 minutes.  Let them cool and then roll them in a kitchen towel.  Don't worry about getting every last bit of the skin off the nuts, only what is loose.  Strain out the skins, chop the nuts coarsely.

Prepare the pie shell, add foil and pie weights and blind bake at 375 ° for 7-8 minutes, just until the pie pastry is set. Do not let the pastry brown at all.  Let cool.

In a large heavy-bottomed saucepan, stir together the sugar and water.  Set the saucepan over medium-high heat. DO NOT STIR THE SUGAR!!!!  Let the sugar come to a boil and continue to cook until it is a golden  brown.  If it browns unevenly, you can move it around by swirling it in the pan.   When the sugar is a rich golden brown, remove it from the heat, stand back and add the butter.  Stir it in with a wooden spoon, then the evaporated milk until smooth. Let cool for 5 minutes and stir in the chocolate.   Set the filling aside to cool for 10 to 15 minutes and then stir in the nuts  Meanwhile preheat the oven to 450°.

Pour the filling into the pie shell and bake for 10 minutes or until the edge is very brown and the center is bubbling.