Check your avocado is ripe before starting this recipe (see cooking tip). Preheat the oven to 200C, fan-forced. Line an oven tray with baking paper. Cut the unpeeled potatoes into 1.5cm-thick chips. Put on the lined tray, drizzle with 2 tsp olive oil, season with salt and pepper and toss to coat. Roast the chips on the upper oven shelf for 20-25 mins until tender.
Step 2 — Prep vegetables
Meanwhile, thinly slice the onions into rounds, then separate into rings. Coarsely chop the avocado. Thinly slice half the tomato. Coarsely chop the remaining tomato.
Step 3 — Make beef patties
Put the beef mince, chipotle (chipotle is a smoky Mexican chilli sauce; use less or omit it if you prefer less heat) and 1 egg yolk in a large bowl and season with salt. Using damp hands, combine well, then shape into 2 equal patties, slightly larger than the base of a bun.
Step 4 — Cook onion and patties
Heat 2 tsp olive oil in a medium frypan over medium-high heat. Cook the onion, stirring, for 5 mins or until soft and golden. Transfer to a bowl and cover to keep warm. Heat 2 tsp olive oil in the same pan over medium-high heat. Cook the beef patties for 3 mins. Turn and cook, covered, for a further 3 mins or until cooked through. Remove from the pan and rest for 3 mins.
Step 5 — Make salad
Meanwhile, combine half the aioli with 2 tsp water in a large bowl. Add the avocado, chopped tomato and rocket, season with salt and pepper and toss to combine.
Step 6 — Get ready to serve
Halve the buns through the middle. Put on an oven tray, cut-side up, and bake on the lower shelf for 5 mins or until lightly toasted. Spread the bun bases with the remaining aioli. Divide the sliced tomato, beef patties and onion among the bases, then sandwich with the bun tops. Serve the burgers with the chips and salad.