Method

Serves 4

Rinse porcini mushrooms then soak in hot water for 30 minutes. Reserving soaking liquid, remove mushrooms, rinse them well under running water, shake off excess water. Chop porcini if large. Strain liquid into a bowl through a sieve lined with a piece of kitchen paper, then strain again.

Wipe button mushrooms with a clean, damp cloth. Cut thickly. Heat a large frying pan over a medium-high heat. When it is hot, add a large knob of butter. Once it has melted and is sizzling, add button mushrooms. Increase heat to high and cook quickly, tossing often, until lightly browned. Don't overcook, the mushrooms should remain firm. Transfer mushrooms to a plate.

Reheat pan over a medium heat. When it is hot, add a small knob of butter. Once it is sizzling, add the drained porcini and rosemary. Cook for 2-3 minutes, stirring often, then add 1/2 cup strained porcini liquid and cook for 10 minutes, letting the porcini liquid evaporate. Season with 1/4 teaspoon of salt and plenty of pepper.

Add red wine vinegar, stir for a minute then add cream and bubble up. Drain button mushrooms and return to pan without any juices which seep out and heat through for 1 minute only. Quickly spoon mashed potato into potato shells and arrange potatoes on individual plates. Spoon mushrooms over prepared jacket potatoes, sprinkle over chives if using, then serve immediately.