Preheat the oven to 200°C/gas mark 6. Place the halved sweet potatoes on a baking sheet, drizzle with 1 tbsp of the olive oil and roast for 40 minutes or until tender and lightly charred. Scoop the flesh from the skin and mash in a bowl with a fork.
Blanch the edamame beans, then whizz in a blender until finely chopped. Add to the mashed sweet potato along with the coriander, 3 spring onions, cumin and smoked paprika. Season to taste and combine well. Shape into 8 thin burgers and allow to cool for 20 minutes.
Meanwhile, brush the mushrooms with a little of the olive oil and grill on high for 5 minutes until tender, turning halfway through. Heat the remaining oil in a large non-stick frying pan, then add the burgers and cook for 7 minutes, turning very carefully just once during cooking.
Combine the avocado, tofu, lime juice, garlic, chilli and remaining spring onions to make a quick guacamole. To serve, place a mushroom on a chopping board, then place a burger on top. Add the guacamole, then another burger. Finish with some rocket and alfalfa shoots, and top with a final mushroom.