Preheat the oven to 450 degrees F (230 degrees C).
Cut the cabbage into quarters and place it on a baking sheet with the round side against the baking sheet (so the cut edges are facing upwards). Drizzle and brush the cut edges with oil.
Roast the cabbage for 20 minutes, until the edges begin to char. Turn the cabbage so the cut side is touching the baking sheet and roast for 20 minutes. Turn the cabbage again and roast until it is charred and softened for an additional 10 minutes. Remove the cabbage from the oven. Let cool slightly, then cut into 1/4-inch (1/2cm) slices.
Beer Braise
Warm the duck fat in a Dutch oven over medium heat. Add the onion slices and cook until softened, about 5 minutes.
Add the sliced cabbage to the Dutch oven and coat in the duck fat. Mix in the beer, vinegar, mustard, and salt. Cover the Dutch oven with the lid and braise over medium heat until the cabbage is very soft, 20 to 30 minutes.
Braise Finishing Liquid
While the cabbage is braising, in a small bowl mix together the Blues Hog Champions Blend Sauce, beer, vinegar, and salt. Pour over the cabbage and continue to braise for an additional 5 minutes.
Garnish
Warm the pumpkin seeds in the maple syrup. Top the cabbage with the pumpkin seeds and sour cream, then serve immediately.