0 Brine the Short Ribs: Season the short ribs evenly with kosher salt. Refrigerate uncovered for at least 1 hour and up to 12 hours. Remove from the refrigerator 30 minutes before searing.
1 Reduce the Wine: Add the red wine and balsamic vinegar to a saucepan. Bring to a simmer over medium heat and reduce by half until slightly thickened and syrupy. Set aside.
2 Sear the Short Ribs: Preheat a Dutch oven or braising pan over medium heat for 5 minutes. Add a thin layer of oil. Sear the short ribs on all sides until deeply golden. Transfer to a plate.
3 Build the Base: In that same pan, add the onion, shallots, garlic, celery, and 1 parsnip to the pan. Cook over medium heat, stirring occasionally, until golden, about 7 to 8 minutes. Stir in the peppercorns, allspice, maple syrup, dried shiitake mushrooms, and miso. Cook for 2 minutes until fragrant.
4 Braise: Return the short ribs to the pan. Pour in the beef broth and the reduced wine mixture. Lay the parsley over the top. Bring to a simmer, cover, and transfer to a 375°F (190°C) oven for 30 minutes. Reduce the oven temperature to 325°F (165°C) and continue braising for about 2 hours, or until the meat is very tender.
5 Strain and Thicken the Sauce: Remove the short ribs from the pan and set aside. Strain and reserve the braising liquid, pressing firmly on the veggies to extract as much liquid as possible. Transfer the liquid to a saucepan and bring to a simmer. Mix the cornstarch with a few tablespoons of the hot liquid to form a slurry, then add gradually to the sauce, stirring until thickened to your liking.
10 Make the Polenta: Bring the broth (or water) and milk to a simmer on high heat. Once boiling, change the heat to low and whisk in the polenta, removing any lumps. Cover and let simmer for 20-25 minutes, stirring frequently. Add cheddar, salt, pepper, heavy cream and mix well. Turn off the heat and add the butter.
6 Fry the Parsnips: Fry the matchstick parsnip in hot oil until golden and crisp. Drain on paper towels and season lightly with salt.
7 Wilt the Spinach: In a large skillet over medium heat, add the spinach, season with salt and pepper, and cook for 1 to 2 minutes until just wilted.
8 Finish: Return the short ribs to the thickened sauce and gently warm through.
9 Serve: Spoon the short ribs and sauce over cheesy polenta. Add the wilted spinach, top with crispy parsnips, and finish with sliced chives.
