Fill and boil your kettle. Peel and slice the onions as thinly as possible. You can use a mandoline or the slicing attachment on your food processor if you have one.

Place a large pan on the heat for a few mins then drizzle in 2 tbsp oil. Add the onions with a good pinch of salt and cook on a low heat for 20 mins, stirring regularly. The onions should be meltingly soft but not coloured. If they start to brown, turn the heat down or transfer the pan to a smaller hob.

While the onions cook, pop the dried porcini mushrooms into a small heatproof bowl and cover with boiling water. Leave for 5 mins to soak. Finely chop the rosemary leaves. Fill and boil the kettle again.

Drain the porcini mushrooms and rinse well under a cold tap. Crumble the stock cube into a jug. Add the rinsed porcini mushrooms and pour over 800ml boiling water. Stir well and leave to infuse and soften.

When the onions have cooked for 20 mins, add 2 tbsp balsamic vinegar and let it bubble up. Add the porcinis, along with their soaking liquid. Scatter in the rosemary leaves and stir. Pop on a lid and simmer for 10 mins.

Taste the soup after 10 mins, adding more salt or pepper if you think it needs them. Ladle the soup into warm bowls and top with the tangy sheep’s cheese to serve.