Preheat the oven to 350 degrees F. In a medium-size bowl, combine the flour and confectioners' sugar. Cut in the butter. Press into a 9x13-inch baking dish. Bake for 15 minutes.
While the crust is baking, in a medium-size bowl, beat the milk, egg, vanilla, and salt. Stir in the toffee chips and walnuts. Spread over the cooked crust and bake for 18 to 25 minutes. Cool completely, then cut into 2-inch bars.