Preheat oven to 400°F.
In a mason jar, combine the chicken broth, 1/4 cup white wine, 1 tablespoon Dijon mustard, 1/2 teaspoon dried thyme, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper. Cover and shake to combine well. If you do not have a jar, use a small bowl and a whisk to combine.
To prepare the cabbage, rinse it and remove the outer leaves. Trim the bottom core to make it even and create a solid base. Place the trimmed core side down on a cutting board and carefully cut the cabbage in half through the core, then cut each half into 4 wedges, keeping the core intact.
Heat the 2 tablespoons of olive oil in a large cast-iron or enamel-coated skillet over medium heat until it shimmers. Add 4 of the cabbage wedges, cut side down, to the pan and drizzle about half of the remaining olive oil over the cabbage slices, to try and evenly coat the cabbage, getting the oil between the layers.
Sear the cabbage until golden to dark brown on the first side, 4-5 minutes. Carefully, flip the wedges and cook until golden to dark brown on the second side, another 3 to 4 minutes. Remove from the skillet and set aside. Repeat with the remaining four wedges, drizzling the remaining olive oil over them as they sear. Carefully, remove the seared wedges from the skillet and set aside.
Add the thinly sliced red onion and minced garlic to the pan. Adjust the heat and cook until the onion is softened, 3 to 5 minutes. If needed, add an extra tablespoon of olive oil.
Add the bay leaves and cook with the onions for about one minute. Add the remaining 1/4 cup of white wine and cook for about one minute.
Return the cabbage wedges to the skillet, cut side down, overlapping them if needed to fit.
Shake the prepared broth mixture and pour it over the cabbage wedges, allowing it to run through the leaves.
Cover with a tight-fitting lid or foil if you do not have a lid for your oven-proof skillet.
Transfer the oven-proof skillet to the oven and roast for 30 minutes.
Uncover and remove from the oven. Spoon broth over the cabbage, basting all the wedges.
Return to the oven and roast, uncovered, until the cabbage is tender, caramelized around the edges, and most of the liquid has evaporated, about 35 to 40 minutes more.
Serve in the pan or on a plate on a serving platter, spooning all the bits and pouring the broth over top.