Crust: Sift together flour, baking powder, and salt. Stir in brown sugar. Cut in butter with a pastry blender until well mixed. Pat evenly into bottom of well-buttered 9×13 inch pan and bake 325 degrees F for 12 minutes.
Filling: Beat eggs until well mixed but not too light. Add brown sugar, flour and salt. Blend. Add corn syrup and vanilla. mix well. Pour over the partly baked crust and sprinkle with pecans. Return to 325 degree F oven and bake 40-45 minutes. Cut into squares while still warm.
Icing: Blend butter, powdered sugar, maple extract and add enough milk to make a thin consistency. Drizzle over the top of cooled cookies.