Adjust rack to top position and preheat oven to 425 degrees. Wash and dry produce.

Cut sweet potatoes into ½-inch-thick wedges. Toss on a baking sheet with a large drizzle of oil, salt, and pepper. Roast on top rack until tender and slightly crispy, 25-30 minutes.

Meanwhile, trim and mince scallions, separating whites from greens. Peel ginger and grate using a zester or the small holes of a box grater until you have ¾ tsp (1½ tsp for 4 servings). Peel and mince or grate garlic.

In a small bowl, combine mayonnaise, scallion greens, ¾ tsp soy sauce, ¼ tsp grated ginger, ¼ tsp sugar, and a pinch of garlic (use 1½ tsp soy sauce, ½ tsp ginger, and ½ tsp sugar for 4 servings).

In a large bowl, gently combine beef*, scallion whites, half the remaining soy sauce (all for 4 servings), remaining grated ginger, and remaining garlic.

Form into two patties (four patties for 4), each slightly wider than a burger bun.

When sweet potatoes have 10 minutes left, heat a drizzle of oil in a large pan over medium-high heat. Add patties and cook to desired doneness, 3-5 minutes per side.

While burgers cook, halve and toast buns.

Spread cut sides of buns with aioli (save some for dipping), then fill with patties, chili sauce, and crispy fried onions.

Divide burgers and sweet potato wedges between plates. Serve with remaining aioli on the side for dipping.