Fill the kettle and boil it. Rinse the celery. Peel the onion. Finely dice them both. Peel the carrot. Chop into chunky slices. Pour 300ml of hot water from the kettle into a measuring jug. Add the porcini mushrooms. Set aside to soak.
Heat 1 tbsp olive oil in a pan. Add the pork. Fry for 5 mins. Turn every so often so the stir-fry strips brown all over.
Add the carrot, onion and celery. Cover. Cook on the lowest heat for 8–10 mins till the veg are soft and glossy looking. Stir now and then.
Rinse the mushrooms while the veg cook. Roughly chop them. Add to the pan. Season. Pop the lid back on. Cook for 5 mins till the mushrooms are soft and juicy.
While the mushrooms cook, peel the Jerusalem artichokes. Slice them into chunks. Rinse the parsley. Pat dry. Roughly chop the leaves.
Stir in the artichokes, the soaked porcini and the water they soaked in. Rinse a sprig of rosemary. Add to the veg. Cover. Simmer for 5-10 mins or till the artichokes are tender. Stir every now and then.
Take the stew off the heat. Stir in 1 tbsp of the crème fraîche to cool it a little, then add the rest of the pot. Taste and adjust the seasoning. If it needs warming through, pop on a low heat for 1 min.
Serve in warmed bowls with a little chopped parsley sprinkled on top.