For the gnocchi, place the dry mashed potato, egg and chives into a bowl and mix well.
Gradually add the flour, beating well between each addition then season with salt and freshly ground black pepper.
Place the dough onto a floured work surface and roll out to a thickness of 2cm/¾in.
Cut the gnocchi into pieces about 2cm/¾in long, then press the top of each one lightly with a fork.
Bring a pan of salted water to the boil, then drop in the gnocchi and return the water to the boil. When the gnocchi rise to the surface, cook for a further three minutes, then drain well and refresh in iced water. Remove the gnocchi from the iced water with a slotted spoon and set aside.
For the stew, season the fish fillets with a little salt. Heat a frying pan until medium hot, add the butter and one tablespoon of the olive oil and heat until foaming.
Add the fish and fry the fillets on each side for two minutes until just cooked through. Remove the fish from the pan and set aside in a warm place.
Heat a sauté pan until hot, add the remaining olive oil and the chorizo and fry for 2-3 minutes, or until the oil from the chorizo begins to run and the chorizo is crisp.
Add the artichokes to the pan, fry for one minute, then add the sherry and chicken stock and bring to a simmer.
Cook for two more minutes or until the artichokes are just tender, then add the gnocchi and gently stir them through the sauce.
Add the cream, simmer for a couple of minutes, then add the tomatoes and most of the chives and chervil. Season with salt and freshly ground black pepper, then add the lemon juice to taste.
To serve, lay the fish on one side of the plate, spoon the chorizo, gnocchi and artichoke stew alongside and scatter over the remaining chives.