Baked Brie Wreath Appetizer

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