Dice 1 onion and add to a large saucepan. Add the 8 cups of vegetable stock. Place 1 tbsp coriander seeds, 1 tbsp fennel seeds, 6 whole cloves and 3 cardamom pods into a wire tea basket and add to saucepan. Add 2 cinnamon sticks and finely sliced ginger. Bring to boil.
Meanwhile, pour boiling water over the rice noodles in a separate bowl and allow to soak for 8 minutes. Chop tofu into ½ inch cubes. Slice button mushrooms. Slice carrot finely on a diagonal. Thinly slice 5 radishes. Slice the ½ red onion into half moons. Slice 5 scallions diagonally. Slice 1 red chili. When the stock is boiling, add tofu, mushrooms, carrot, ½ of the scallions, radishes, soy sauce, hoisin sauce, and bring to a boil again.
To assemble dish, place a handful of drained noodles into a bowl and ladle over the broth. Add chopped cilantro, mint, red chilli, scallions, bean sprouts and red onion to taste. Finish with a squeeze of fresh lime.