For a growing number of American households, Teflon-coated pans, copper pots, or anything else for that matter other than a handcrafted cast iron skillet, would be, well, an outcast in the kitchen. Crazy as it seems, the people who make this heavily weighted and highly popular custom-made cookware are willing to face furnaces burning at 2300 degrees Fahrenheit on a hot summer’s day, inside an old mill building they bought with their life savings, just to put one in your kitchen. “It can be a little miserable at times,” said Liz Seru, who owns Borough Furnace with her husband, John Truex. About 10 years ago, they converted an old turbine blade factory in Upstate New York into a foundry to pursue their love for cast iron cookware. At the start, Seru, an artist, and Truex, who holds a degree in metal casting, bought vegetable oil off Craigslist to run their …