Stir the sugar, salt and melted butter with a fork. Add the egg yolk and mix well. Add the flour and stir until the crust is moist clumps. Firmly press the dough into a greased 9×13 pan, making an even layer. Refrigerate the crust for 20 minutes.

Bake the crust at 350 degrees Fahrenheit for 20 to 25 minutes, until lightly golden brown on top. Let the crust cool completely while you prepare the caramel.

In a heavy-bottomed saucepan, combine the butter, brown sugar, corn syrup and vanilla. Cook over medium heat, stirring frequently. Bring to a boil. Stop stirring and allow to boil for four minutes.

Pour over the crust and cool completely. Refrigerate until the caramel is set, about one hour.

Bring to room temperature and cut into 2×1-inch bars. Freeze bars for another hour and dip into melted milk or parve chocolate.