Meanwhile, heat a drizzle of oil in a large pan over medium-high heat. Add onion and season with salt and pepper. Cook, stirring, until softened and lightly browned, 8-10 minutes. (If onion begins to brown too quickly, stir in a splash of water.) Add ¼ cup water and 1 tsp sugar (½ cup water and 2 tsp sugar for 4 servings). Cook, stirring, until onion is caramelized and jammy, 2-3 minutes more. Turn off heat; transfer onion to a small bowl. Wash out pan.

While onion cooks, in a second small bowl, combine garlic, 2 TBSP mayonnaise (4 TBSP for 4 servings), and a pinch of chipotle powder (taste and add more if you like). Season with salt and pepper. Form beef into two equal-size balls (four balls for 4); season all over with salt and pepper.

While onion cooks, in a second small bowl, combine garlic, 2 TBSP mayonnaise (4 TBSP for 4 servings), and a pinch of chipotle powder (taste and add more if you like). Season with salt and pepper. Form beef into two equal-size balls (four balls for 4); season all over with salt and pepper.

Heat a drizzle of oil in the pan used for onion over medium-high heat. When pan is very hot, add beef. Firmly flatten each ball with a spatula to create very thin patties. (Don’t worry if the patties aren’t perfectly round—those irregular edges will turn deliciously crispy!) Cook to desired doneness, 3-4 minutes per side. Transfer patties to a plate; carefully pour out grease from pan.

Halve buns. Melt 1 TBSP butter (2 TBSP for 4 servings) in pan used for patties over medium-high heat. Add buns, cut sides down; cook until cut sides are golden brown and toasted, 1-2 minutes.

Divide toasted buns between plates; fill with patties, caramelized onion, and chipotle aioli. Serve burgers with potato wedges and, if you’ve got some on hand, ketchup on the side for dipping.