Baked Brie Wreath

Name: Baked Brie Wreath
Cuisine: European, Mediterranean, French
Ingredients: 2 tablespoons butter; 2 large sweet onions, quartered and thinly sliced; 2 tablespoons honey, plus more for serving; 1 tablespoon fresh thyme leaves; 2 cups fresh or frozen cranberries, thawed if frozen; 1/2 teaspoon kosher salt, plus more for baking; 1/4 teaspoon black pepper; 1 tablespoon balsamic vinegar; 1 sheet puff pastry, thawed; 8 ounces triple cream brie, thinly sliced; 1 cup walnuts, toasted and finely chopped; 1 egg, beaten