Preheat the oven to 275°F (135°C). Season the pork with salt and pepper to taste. Heat a medium oven-safe pot over medium-high heat. Add the oil and butter. When the butter stops foaming, add the pork, in batches if necessary, so it’s in one layer with space in between. Sear, turning occasionally, until golden brown on all sides, about 10 minutes total. Remove the pork to a plate, reduce the heat to medium, then add the shallot, celery, fennel, garlic powder, thyme sprig, and 1/2 teaspoon salt and 1/4 teaspoon pepper. Cook, stirring often, until the shallots and fennel are wilting, about 5 minutes.
Add the half & half, 1 of the sage leaves, and the bay leaves, lemon zest, cinnamon stick, and baking soda; stir to combine. Return the pork to the pot, along with any collected juices. Cover and bring to a simmer. Transfer to the oven, and cook, covered, for 2 hours, turning the pork a few times along the way.
Remove the pot from the oven, remove the lid, and gently remove the pork to a plate. Remove and discard the cinnamon stick, thyme sprig, and bay leaves. Add to the pot of sauce the kale and 1/4 cup water. Bring the liquid to a simmer over medium heat and toss the kale to coat. Cover and let simmer until the kale is very tender and wilted, stirring a few times during cooking, about 10 minutes.
Meanwhile, line a small plate with a paper towel. Heat a small skillet over medium-high heat. Add a 1/4-inch layer of olive oil and heat until the oil starts shimmering. Add the sage leaves and fry for 45 seconds, turning them with a fork after 30 seconds. Immediately remove to the paper towel to drain and crisp.
Rough-shred the pork using 2 forks to pull the meat apart. Divide the creamy kale among 6 dinner plates, top each with one-sixth of the pork, garnish with the crispy sage leaves, and enjoy.