Preheat oven to 350°F.

In a bowl, stir together the flour, icing sugar and salt. Cream in the butter until the mixture turns into a pliable dough. It will look like shortbread. Pat the dough evenly by hand into the bottom of a buttered 9"x13" pan.

Bake for 11 minutes. Let cool slightly before adding filling.

While the base crust is baking, beat together all the filling ingredients until smooth, scraping down the sides of the bowl. Mix well.

Pour over the hot baked base. Return the squares to the oven immediately. Bake at 350°F about 25 minutes until pale gold in color. During last 5 minutes, put a cookie sheet below the baking pan to be sure the bottom does not burn.

Remove from the oven. Let cool completely in the pan on a cake rack.

Cut into squares. Store in tightly covered container.

Makes about 24 squares.