Combine cake mix and nuts (optional) in large bowl. Stir in butter. Stir in ⅔ cup evaporated milk (batter will be thick). Spread half of batter into ungreased 13 x 9-inch baking pan. Bake in preheated 350°F oven for 15 minutes.

Cook caramels and remaining evaporated milk in small saucepan over low heat, stirring constantly until caramels are melted. Sprinkle chocolate chips over hot base; drizzle with caramel mixture.

Drop remaining batter by heaping teaspoon over caramel mixture. Bake at 350° F. for 25 to 30 minutes or until center is set. Cool completely in pan on rack. Cut into bars. Makes 4 dozen.