Preheat oven to 425°; slice potatoes into ¼-inch rounds; toss with oil, salt/pep, add to sheet pan in 1 layer + bake 20 min, flipping ½ way through; remove from pan to cool

Heat lightly oiled skillet over medium; cook burgers 10 min, flipping every 1-2 min to avoid burning until hot + fully cooked

Meanwhile, wash + dry a few lettuce leaves; thinly slice ¼ of onion; toast 2 buns til warm + golden; spread aioli onto each bun

Divide burgers to buns with lettuce + onion; serve with sweet potatoes on the side