2In a medium bowl, combine 1/2 cup of the butter with the cake mix and egg. Work the mixture with your hands until everything is well blended. The mixture will be crumbly. Press the mixture evenly into a 10 x15 inch jellyroll pan.
3Bake for 10 minutes in the preheated oven. Remove and cool for 10 minutes.
4In a saucepan , combine the remaining 1/2 cup of butter with the evaporated milk and caramels, over medium heat. Stir occasionally until smooth. Remove from heat and pour the mixture over the baked crust, turning the pan from side to side so that it is evenly coated.
5Return to the oven, and bake for 15 to 20 minutes, until it is bubbly all over. Cool and drizzle with icing. Allow icing to set before cutting into squares.
6To make the icing, stir together the confectioners' sugar with the water and vanilla until smooth. If the icing is too thick, add more water. If it is too thin, add more confectioners' sugar.