Method

• 1.
  Preheat oven to 180°C. For the chipotle mayonnaise, combine all ingredients in a bowl and chill until required.
• 2.
  For the oven-baked eschalots, heat a frypan over high heat, add eschalots cut-side down and cook, without stirring, for 3-5 minutes or until blackened but still firm. Transfer eschalots cut-side down to a baking tray, drizzle with vinegar and place butter evenly around the eschalots. Bake for 15 minutes or until tender. Stand until cool enough to handle, then peel and discard skins.
• 3.
  Meanwhile, place sweet potato, zucchini, butter and 1⁄2 tsp salt flakes in a bowl, stirring until well combined. Divide sweet potato mixture into sixths, use a fork to twirl each portion into a small pattie, and place on a tray.
• 4.
  Heat 1cm oil in a frypan over medium- high heat. Working in two batches, shallow-fry patties for 5 minutes on each side or until starting to develop colour and look crispy (if you like, you can use food rings so the patties hold together better, in which case you should put the food ring straight into the frypan and fill it with sweet potato mixture). Transfer patties to paper towel. Then put them into an ovenproof dish and bake for 5–10 minutes or until tender.
• 5.
  Preheat a barbecue grill or chargrill pan over medium-high heat. Spread extra butter on the cut-side of burger buns and grill cut-side down for 1-2 minutes or until grill marks are visible.
• 6.
  Divide rainbow chard between bun bases and top with patties, shallots and a spoonful of chipotle mayonnaise. Scatter with edible flowers, if using, and top with bun lids to serve.