Place the porcini mushrooms in a small bowl, add 250ml boiling water and leave to soak for 15 minutes.
In the meantime, clean the mushrooms and cut into quarters. Peel and chop the garlic; peel and finely dice the onion. Wash the thyme, shake dry and pick off the leaves.
Heat the oil in a pan and fry the mushrooms over a high heat, stirring. Add the onions, garlic and thyme and fry for about 1 minute.
Drain the porcini mushrooms, squeeze out the excess liquid and chop roughly.
Pour the soaking water into the pan through a fine sieve, then add salt and black pepper.
Add the porcini mushrooms to the soup and bring to the boil. Reduce the heat and simmer for 20 minutes.
Remove half the soup and puree until smooth with a stick blender or food processor. Return to the pan and bring to the boil.
Squeeze the juice from the lemon. Season the soup with 1-2 tbsp lemon juice to taste. Stir in the soy cream and reheat briefly. Season with salt and pepper and serve immediately.