In a saucepan, combine the dark brown sugar, 1/4 cup butter and milk. Stir over low heat until butter is melted. Pour into an ungreased 8" square baking pan; sprinkle evenly with pecans. In a mixing bowl, cream light brown sugar and remaining butter; add eggs. Stir in flour, vanilla and salt until moistened. Spread over pecans. Bake at 350 degrees for 30-35 minutes or until brownies test done. Cool 5 minutes in pan; invert onto a tray or serving plate. Cool slightly before cutting.