For the crust: In a big bowl (or food processor) mix the flour and sugar. Rub in the butter until the mixture is crumbly. Add the yolk to form the dough. If it's necessary add 1 tsp iced water. Do not knead, just press it together.Shape it into a disc, wrap it in plastic and chill for at least 30 minutes. Preheat the oven at 350°F. Remove the dough from the fridge and let it stand for a few minutes so it does not break up. Roll it out on a floured surface, fit it into a 9-inch pie plate and trim the excess.
Cover the crust with tin foil, fill it with beans (or any other legume) to weigh it down and prevent it from rising, and bake it for 10 minutes. Then remove the beans and the foil, and bake for 5-10 more minutes until golden brown.
For the filling: mix the melted the butter, corn syrup, eggs, brown sugar and cornstarch. Add the pecans and mix it well.
Sprinkle the chocolate over the crust pie and pour the filling over the top. Bake for about 40-60 minutes, you may need to cover the crust if it starts to get dark quickly. Let cool completely before cutting.
