Preheat oven to 350. Line a 10x15 inch cookie pan with parchment. Cream butter and sugar until light and fluffy, then beat in salt and vanilla. Reduce mixer speed to low and mix in flour (dough will be crumbly). Fold in chips. Press mixture into your pan and bake until golden, about 20 minutes. Cool in pan about 5 minutes, then transfer to a cooling rack. When completely cool, break into pieces or cut with a serrated knife.