Place the dried porcini mushrooms in a small microwave-safe bowl and add the Marsala to cover. Heat for 30 seconds to 1 minute, depending on the strength of your microwave.

Set aside to allow mushrooms to soften.

Heat the oil and butter in large stockpot over medium heat.

Add leek, carrot, and celery; cook, stirring often, for 8-10 minutes until tender, but not browned.

Add the fresh mushrooms and cook, stirring often, for 5 minutes until softened.

Strain the porcini mushrooms, reserving the Marsala.

Rinse the porcini to remove any sand and grit, then coarsely chop them and add them to the pot. Sauté them for a minute longer.

Stir in chestnuts and stock, cover and bring to the boil.

Reduce heat and gently simmer, uncovered, for 45 minutes.

Remove from heat. Add the reserved Marsala.

In batches, purée soup in a blender until very creamy.

Pour into a clean pot. Bring back to a simmer and stir in the light cream.

Ladle into bowls and garnish each serving with a slice of mushroom.