Which item features sautéed mushrooms and onions as toppings?

The Smokehouse Burger is the correct choice because it is specifically designed to include a combination of sautéed mushrooms and onions as toppings. This burger features a grilled beef patty topped with these flavorful ingredients, which enhance the overall taste by adding umami and texture. The addition of sautéed mushrooms and onions is characteristic of the Smokehouse Burger, creating a savory profile that sets it apart from other burger options on the menu.

Other items may have their own unique toppings or flavor combinations, but the presence of sautéed mushrooms and onions is a defining feature of the Smokehouse Burger, making it the correct answer in this scenario.