Which of the following ingredients is used as a garnish in the Tuna Stack?

The ingredient used as a garnish in the Tuna Stack is shredded nori. Shredded nori adds a unique texture and a hint of umami flavor that complements the fresh tuna. Nori, which is dried seaweed, is commonly used in Japanese cuisine and enhances the presentation of the dish, making it visually appealing while contributing to the overall taste profile.

In contrast, while pickled ginger is often associated with sushi as a palate cleanser, it is not typically used as a garnish in this particular dish. Toasted sesame seeds can add flavor and crunch to many dishes but are not the primary garnish in the Tuna Stack. Chili flakes, known for their heat, might be used in some recipes, but they are not a standard garnish for this specific dish as they could overpower the delicate flavors of the tuna.