Preheat oven to 375 degrees. With an electric mixer, cream together the butter and the sugar. Add the egg and mix until well combined. Stir in the flour and combine to make a dough.
Pat the dough into a 9-inch pie plate.
For the topping
In a small saucepan, combine the chopped pecans, sugar, butter, milk, and chocolate. Heat over low heat until chocolate melts.
Pour the chocolate pecan mixture over the pie dough. Bake for 30 minutes. Turn the oven off and let the pie sit for an additional 15 minutes. Serve while still warm.