Peel and finely chop or grate the garlic and ginger. Peel and thinly slice the shallot. Slice the mushrooms.
Pour 1 tbsp oil into a pan and bring to a medium-high heat. Slide in the mushrooms and shallot and cook for 3-4 mins, stirring occasionally, till golden.
Add the garlic and ginger and continue to cook for a further 1 min. Pour in 850ml boiling water and spoon in the miso paste. Stir well to combine. Return to the boil, then add the spaghetti. Cook for a further 10-12 mins, till the strands are soft with a little bit of bite.
Meanwhile, strip the kale leaves from the tough stalks. Discard the stalks and finely shred the leaves.
When the spaghetti has 4 mins left, stir in the kale leaves and simmer for the remaining 4 mins. Have a taste and add salt or pepper if needed, then ladle into deep bowls and serve.