In a large bowl, mix together cake mix, chopped pecans, 1/3 cup evaporated milk, and melted butter. Stir together until totally combined. Mixture will be very thick.
Press half the mixture into a well-greased 9 x 9 inch square baking pan. Bake for 8 to 10 minutes. Remove pan from oven and set aside.
In a double boiler (or a heatproof bowl set over a saucepan of boiling water) melt caramels with additional 1/2 cup evaporated milk. When melted and combined, pour over brownie base. Sprinkle chocolate chips as evenly as you can over the caramel.
Turn out remaining brownie dough on work surface. Use your hands to press it into a large square a little smaller than the pan. Use a spatula to remove it from the surface, then set it on top of the caramel and chocolate chips.
Bake for 20 to 25 minutes. Remove from pan and allow to cool to room temperature, then cover and refrigerate for several hours. When ready to serve, generously sift powdered sugar over the surface of the brownies. Cut into either nine or twelve helpings, and carefully remove from the pan.