1. Heat a grill to medium and lightly grease grate (alternatively, set up an electric griddle to 400ºF).

2. In a medium bowl, combine all patty ingredients. (It’s very moist, don’t worry!) Form into 5 patties, about 5 inches in diameter. Refrigerate, covered, for 30 minutes.

3. Meanwhile, prepare sauce: In a medium saucepan, whisk together all sauce ingredients except arrowroot. Place on high heat, bring to a boil, then reduce to a simmer, cooking until mixture reduces by half, about 15 minutes.

4. In a small bowl, whisk together arrowroot and ¼ cup water; add to sauce. Whisk until thickened, about 1 minute. Remove from heat; set aside.

5. Carefully transfer patties to grill with a metal spatula and cook for 4 to 5 minutes. Flip and pour 1 tbsp sauce on each burger. Smear sauce on patty using a separate spoon (to avoid contamination). Cook for another 4 minutes, or until cooked through.

6. Meanwhile, brush pineapple on both sides with oil and grill until marks appear, about 3 minutes. Flip and repeat.

7. Place patties on buns, each with a slice of grilled pineapple, and toppings, including extra teriyaki sauce, if desired.