Blend the grouper, thyme, cream and thyme together until a smooth mousse, open the salmon like a butterfly, place the mousse in the middle and seal again. Roll in cling film and poach in fish stock without allowing to boil. Once cooked remove from stock allow to rest for few minutes then remove cling film. Meanwhile, prepare the sauce. On low heat, sauté the chopped garlic, onions, star anise and fennel in salted butter until transparent. Add stock and cream and simmer until thickened, pass through a strainer and remove star-anise. Next, cut the courgette lengthwise in thin slices and grill. Cut the sweet potato into pieces and boil till soft. Grill on a griddle pan. Roughly cut the cabbage in thick slices sauté in a pan. To serve, spoon the cabbage on a plate and layer the grilled vegetables on top. Finally, top off with the cooked fish and serve.