French Onion Cabbage Steaks

Name: French Onion Cabbage Steaks
Ingredients: 1 medium head green cabbage; 1 tablespoon extra-virgin olive oil; ½ teaspoon ground pepper; ¼ teaspoon salt; ¾ cup finely grated Gruyère cheese; 5 tablespoons unsalted butter , softened, divided; 1 small yellow onion , thinly sliced; ⅔ cup lower-sodium beef broth; 1 teaspoon minced garlic; 1 teaspoon chopped fresh thyme , plus more for garnish; 1 tablespoon sherry vinegar; 1 teaspoon reduced-sodium Worcestershire sauce; ½ teaspoon salt; ¼ teaspoon ground pepper