Use a spiraliser, mandolin or knife to cut the sweet potato into noodles.
Heat 3 tsp of the oil in a large frying pan. Cook half the sweet potato, stirring, for 5-7 mins or until softened. Transfer to a medium bowl. Repeat with 3 tsp of remaining oil and the remaining sweet potato. Set aside for 15 mins to cool.
Add egg to sweet potato and season. Toss to combine. Divide among 8 greased 10cm ramekins or bowls. Cover with greased plastic wrap. Place a can or other ramekins on sweet potato to flatten and form a bun. Chill for 30 mins.
Meanwhile, combine mince, taco seasoning and two-thirds of coriander in a bowl. Shape into four 10cm patties.
Mash avocado in a small bowl until smooth. Stir in tomato, lime juice and remaining coriander. Season.
Heat remaining oil in a large frying pan over high heat. Remove sweet potato buns from ramekins. Cook, in batches, for 2-3 mins each side or until golden and cooked through. Transfer to a plate and cover to keep warm.
Add patties to pan and cook for 2-3 mins each side or until cooked through.
Place half the sweet potato buns on plates. Top with kale, onion, patties, avocado mixture, jalapeños and chilli sauce. Sandwich with remaining buns.