In a large bowl, combine flour and sugar. Cut in butter until mixture resembles coarse meal. Press firmly onto the bottom of a greased 13x9-in. baking dish. Bake at 350° for 15 minutes. , Meanwhile, in a large bowl, beat the milk, egg, vanilla and salt until smooth. Stir in toffee bits and pecans; spread evenly over baked crust. , Bake until lightly browned, 20-25 minutes longer. Cool. Cover and chill; cut into bars. Store in refrigerator.