Bring the crème fraîche to the boil with 250ml water and the orange juice. Stir in the polenta and semolina, season with salt and sugar. Remove from the heat and stand for 15 minutes, stirring regularly.
Peel the oranges with a knife, removing all the white pith.
Cut out the orange segments between the separating skins. Put the segments in a small bowl and squeeze over the remaining orange juice.
Drizzle the orange segments with the Grand Marnier and marinate for about 20 minutes.
Wash the fennel and dice finely. Sprinkle with salt and sugar and saute briefly in a pan. Wash the fennel greens, shake dry and set aside.
For the sauce, peel and finely dice the shallots. Heat the butter in a pan and cook the shallots and fennel seeds until translucent. Deglaze with the wine and fish stock. Reduce to about one-third, then stir in the double cream, bring to the boil and season to taste.
Pass the sauce through a fine sieve and keep warm.
Rinse the turbot, pat dry, skin and remove the bones.
Cut the fillets into pieces of approx. 50g and season with salt and pepper. Sauté briefly in the hot butter.
Turn the fillets, fry for 1 further minute, then spread on a baking sheet and keep warm in a low oven.
Roll out 2-3 tbsp of the polenta mixture between 2 layers of baking paper and cut into strips.
Shape the remaining mixture into balls with a teaspoon.
Cook the strips and the balls in a pan of hot oil at 170°C for 2-3 minutes. Drain on kitchen paper. Heat the fennel cubes in their juice and allow to stew for 5 minutes. Serve the fish, the drained orange segments and the polenta balls on plates. Scatter over the fennel cubes, the sauce and the crunchy polenta stripes. Garnish with the fennel greens.