How to Make It
Preheat the oven to 400°. In a large roasting pan, toss the cabbage wedges with the olive oil and season with salt and pepper. Arrange the wedges cut side down in a single layer and scatter the garlic and rosemary sprigs around them. Cover tightly with foil. Bake for about 45 minutes, until the cabbage cores are tender. Uncover and bake for about 20 minutes longer, turning once, until the cabbage is brown around the edges.
Arrange the cabbage on a platter and tent with foil. Strip the rosemary leaves from the stems; discard the stems and garlic.
In a medium skillet, toast the walnuts over moderate heat, tossing, until lightly browned, 5 minutes. Let cool, then coarsely chop.
In the same skillet, melt the butter. Add the chopped walnuts and cook over moderate heat, stirring, until the butter turns medium brown and smells nutty, about 5 minutes. Add the rosemary needles and cook, stirring, until crisp, about 1 minute. Reduce the heat to low, stir in both vinegars and cook until the dressing is slightly reduced, about 2 minutes. Season with salt and pepper. Spoon the dressing over the cabbage wedges and serve.
Moscatel vinegar, a lightly sweet and tangy, Spanish white balsamic–like vinegar, is available at specialty food stores and online at taylorsmarket.com.