For the mushroom stock, heat the oil in a large pan. Cook the shallot and garlic until soft, add the mushroom and turn up the heat. Mix in the curry powder. Cook for a minute then add the thyme and stock. Bring to the boil then simmer for 30 minutes. Take off the heat. Allow to infuse for 30 minutes then pass through a fine cloth into a clean pan. Heat until reduced in volume to about 250ml/9fl oz and a rich mushroom flavour is achieved.
For the shellfish stock, discard any open shellsfish that do not close when given a sharp tap. Heat a large, lidded pan and add the shellfish, wine and water. Cover with the lid, shake the pan and cook for 3 minutes, or until the shells open and a good amount of stock has formed. Pour into a large strainer over a bowl. Allow to drain. Discard any shells which have not opened.
When cooled pick the meat from the shells into a clean bowl and set aside. Strain the stock through a fine sieve and then through a fine wet cloth or mesh to make sure there is no sand or grit.
Heat the stock in a pan over a high heat until it is reduced in volume to about 250ml/9fl oz and has a strong shellfish flavour. Set aside.
For the vegetables, heat half the butter in a pan and cook the wild mushrooms gently until tender.
Blanch the turnip tops in boiling water for a few seconds. Pat dry. Heat the remaining butter in a clean pan and cook the turnip until tender. Finish with a squeeze of lemon juice.
For the sea bass, heat a frying pan and add the oil. Once hot add the fish skin side down. Cook on each side for 2 minutes. Remove from the pan and allow to rest.
Mix the mushroom and shellfish stocks to make a broth. Add the mushrooms, the meat from the shellfish and the fregola.
To serve divide the broth between serving bowls. Dress with the turnip tops and add a piece of sea bass.