Preheat oven to 350 degrees F. Grease a 13x9-inch baking pan.
In a large mixing bowl, use an electric mixer to combine the brown sugar, butter, egg yolk and vanilla; blend in the flour and salt. Press the mixture into the prepared pan. Bake 25 to 30 minutes or until lightly browned. Remove from oven; Immediately sprinkle the chocolate chunks onto the crust. Let stand until softened (about 5 minutes). Spread evenly over the crust, and sprinkle with pecans.