Peel and finely dice your garlic and onion. Then roughly slice your assorted mushrooms into 1/2 cm lengths.
Heat the sunflower oil in a deep pan over a medium heat. Toss in the chilli flakes and toast for a minute. Then pour in your onion and garlic and fry for 3 minutes or so until the onion is soft and see-through.
Add your mushrooms to the pan with 2 tablespoons of soy sauce. Fry for 3 - 5 minutes until the mushrooms have nicely reduced and browned. Then remove 1/2 the mushrooms and reserve for later.
Add one of the cans of black beans to the pan, along with the miso paste, five spice, garlic powder, vinegar, remaining soy sauce and sugar. Cook for a minute or two, mixing to coat the onion in the spice mixture.
Take the pan off the heat and pour into a blender. Blitz into a smooth paste and then return to the pan along with the vegetable stock. (Note: depending on your blender you may have to cook your mixture before blitzing to prevent unwanted kitchen explosions. If this is the case cool the pan in the bath off cold/ice water before blending)
Return the pan to the heat and bring to the boil. Tip in the noodles and turn down to a simmer, cook the noodles to packet instructions until soft but still aldente.
Add the remaining can of black beans and reserved mushrooms, cook for a few minutes more just to heat through the beans and mushrooms. Take the pan off the heat and juice the lime into the pan. Season the broth to taste with a dash or two more of soy sauce.
Serve the broth in deep soup bowl and garnish with whatever takes your fancy and is in your pantry/fridge. I tend to reach for coriander and spring onions when plating, but some other things that I've found work well are - finely sliced raw carrot and ginger or watercress and bean sprouts.