While the brownie layer is baking, in a double boiler (or glass bowl set over a bowl of simmering water) combine the caramels and the remaining 1/2 cup evaporated milk. Stir occasionally until the caramels are totally melted and the mixture is smooth. Pour the caramel mixture over the first baked layer, spreading so it's evenly distributed. Sprinkle the chocolate chips all over the top.