Preheat oven to 425°F.
In a medium bowl, combine herbs de provence, celery salt, smoked paprika, sea salt, pepper and vegetable oil. Rub the mixture all over the cut sides of the cabbage quarters.
Heat a large cast iron pan or an oven-safe skillet with at least 2-inch sides over medium heat. Once hot, add the cabbage wedges cut side down and sear until lightly charred, about 4 to 6 minutes. Depending on the size of your pan, you may need to sear the cabbage in batches. You don’t need to sear them too dark because they will get roasted in the oven later. Once seared, remove the cabbage wedges and set aside. You'll make the braising liquid in the same pan.
To make the braising liquid, measure out the vegetable stock and non-dairy milk in the same liquid measuring cup. Melt the vegan butter in the pan, turning the heat down slightly if needed. Once melted, add flour and stir until no dry flour remains.
Whisk in dijon mustard, vegan worcestershire, apple cider vinegar and maple syrup. Once combined, slowly whisk in the vegetable stock and non-dairy milk. Add cinnamon stick and fresh sage including the stem, and allow liquid to come to a low simmer, about 7 minutes. Whisk frequently and allow it to simmer for another 5 to 6 minutes until it thickens slightly. It should just coat the back of a spoon. At the end whisk in sea salt, red chili flakes, and nutmeg.
Nestle the green cabbage wedges, cut side up so they’re sticking out of the liquid. Spoon some of the braising liquid all over the cabbage so it goes in between the cabbage leaves. Roast for 45 minutes until the cabbage is tender. You can tell by sticking a knife into the center of the largest wedge. If there’s no resistance, it’s ready. Serve in a large shallow serving bowl with the braising liquid. Sprinkle pumpkin seeds or chopped pistachios on top as garnish.