I love to cook on cast iron and I also used to do brazing with oxy-acetylene or oxy-propane torches. (I built a couple of bicycles like that.) I have copper wire and I have found that copper can be "brazed" onto steel using flux and the gas torch in the same way that I can braze with brass. So I would think that one could take a cast iron skillet and place it upside down in the right furnace. Use brazing flux and copper to "braze" the copper onto the base of the skillet. Some added wall might be needed to prevent the melted copper from flowing off the bottom of the skillet. Maybe this could also be done with a hand held gas torch if the skillet did not crack from uneven heat and if the copper could flow flat enough. Brazing is like soldering; the iron base metal dissolves slightly into the molten metal at the metallic boundary so it is a very tight bond.
