Preheat oven to 375 degrees F.
Season 1 bone-in pork loin roast generously with kosher salt and freshly ground black pepper on both sides. If possible, let it sit overnight and bring to room temperature prior to cooking.
Place a large oval cast iron pan over medium-high heat and add 1/4 cup blended oil. Once heated, add the roast to the pan fat-side down and sear, about 2 minutes. Flip to sear on the other side, another 2 minutes. Flip to sear any remaining side, another 2 minutes.
For the cabbage:
Meanwhile, divide the cabbage, onions, Fresnos, toasted caraway seeds, dried chile, salt, and orange juice between 2 bowls. Toss to combine.
Remove the pork from the pan and place onto a baking sheet. Deglaze the pan with about 2 cups chicken stock and use a wooden spoon to scrape the bottom. Add the cabbage mixture and top with the seared pork. Leave uncovered and place into the oven for about 45 minutes to 1 hour or until an instant-read thermometer reads between 140 to 145 degrees F internal temperature.
When ready, remove the pork from the oven and place onto the stovetop or heatproof surface. Lean the pork again the side of the pan. Place the semi-chilled champagne bottle into the pan and take the cage off the top. You can let the top pop on its own or loosen it slowly with a kitchen towel. Allow some of the champagne, about 2 cups, to spill into the pot.
Remove the pork from the pan and allow to rest briefly on a cutting board. Taste and season with salt. Stir in the mustard and the sherry vinegar. Remove the pork loin from the bone and slice. Place the cabbage onto a family-style platter. Fan the pork slices around the cabbage. Carve between the bones and add the bones to the platter. Garnish with the orange zest and cilantro leaves and spoon the pan sauce around the pork.