In a large bowl, combine the flour, brown sugar, butter and salt; blend with an electric mixer on low speed until mixture resembles coarse crumbs.
Press the mixture into the prepared pan; bake 10 minutes.
Meanwhile, combine the corn syrup, butterscotch chips, butter, water, and salt in a 2-qt. saucepan. Cook over low heat, stirring constantly, until the chips are melted and the mixture is smooth (4-7 minutes).
Stir in the cashews until well coated.
Spread cashew mixture evenly over the hot crust; coninue baking 10-12 minutes or until golden brown.