1 Grease a 13x9x2-inch baking pan. Set aside.
2 In a large mixing bowl beat the 3/4 cup butter or margarine and the brown sugar with an electric mixer on medium speed until combined. Add the egg yolk; beat well. Using a spoon, stir in the flour and salt until well mixed. Using floured hands, press the dough into the bottom of the prepared pan. Bake in a 350° oven about 20 minutes or until light brown. Set on a wire rack while preparing the filling.
3 For filling, in a heavy medium saucepan heat and stir the sweetened condensed milk and the 2 tablespoons butter or margarine over medium heat until bubbly. Cook and stir for 5 minutes more. (Mixture will thicken and become smooth.) Stir in the vanilla. Spread filling over the baked layer. Bake for 12 to 15 minutes more or until top
layer is golden brown.
4 Sprinkle the baked layers evenly with semisweet chocolate pieces. Bake for 1 to 2 minutes more or until chocolate pieces are shiny and melted. Remove from oven; set on a wire rack. Using a flexible spatula, immediately spread the chocolate evenly over baked layers. Sprinkle with brickie pieces or pecans. Cool completely on wire rack. Cover and refrigerate until chocolate is set.
5 To cut triangles, cut into rectangles (about 3x2 inches each), then cut each rectangle diagonally. Cover and store any leftover triangles in the refrigerator for up to 1 week.