Preheat your oven to 350º. In a large bowl, mix together the cake mixes, chopped pecans, 2/3 cup evaporated milk, and melted butter. Stir together until totally combined (mixture will be very thick).
Press half the mixture into a well-greased 9×13 inch square baking pan. Bake for 8 to 10 minutes, remove pan from oven and set aside.
Meanwhile, in a double boiler (or a heatproof bowl set over a saucepan of boiling water) melt caramels with remaining cup evaporated milk. When melted and combined, pour over brownie base then sprinkle chocolate chips as evenly as you can over the caramel.
Turn out remaining brownie dough on work surface and use your hands to press it into large sections. Place the sections on top of the caramel as evenly and completely as you can.
Bake for 20 to 25 minutes then allow to cool to room temperature. Cover and refrigerate for several hours or overnight. When ready to serve, generously sift powdered sugar over the top of the brownies. Cut and carefully remove from pan.