Soak the dried ceps in the boiling water for 30 minutes. Drain the ceps well, retaining the liquid. Discard the ceps.
Sauté the leek and garlic in the olive oil in a large pan for 2–3 minutes. Add the parsnip, carrot, and Portobello mushrooms and sauté for a further 5–6 minutes until the mushrooms emit their liquid and begin to soften.