In a large bowl beat butter and sugar until fluffy, beat in eggs 1 at a time, add vanilla, stir in salt, then flour 1 cup at a time, then stir in chocolate chips.
Using your hands or a spatula press onto an ungreased 12 inch (30 centimeters) rimmed pizza pan or baking sheet, press to cover the whole pan.
Bake in a pre-heated oven for approximately 30-35 minutes or until golden and firm to the touch. Remove and let cool in pan on a wire rack. Leave cookie in pan to decorate.
FOR THE ICING
In a medium bowl beat butter at medium speed until smooth. Add 1 cup of powdered sugar, beat at medium until light and fluffy. Add water, beat on low until well blended, scraping down side of bowl once, then beat in the second cup of powdered sugar until mixture is creamy. Makes 1 cup.