Remove the peel from the orange, blood orange and grapefruit, fillet them and collect the juice. Soak 2 and 4 sheets each of gelatin in cold water. Wring out the limes.
Stir yogurt, crème fraîche, lime juice and powdered sugar. Whip the whipped cream until stiff. Melt the 4 sheets of gelatine in a saucepan, add a small amount of whipped cream and fold into the whipped cream. Now gently fold the whipped cream into the yogurt mixture.
Place a baking dish in iced water and line with plastic wrap. Pour half of the yogurt mixture into the mold. Slightly heat the juice of the citrus fruits and let the remaining gelatin melt in it. Next, mix with the fruit fillets.
Pour everything on the already well precooled yogurt mixture in the mold and spread evenly. Dress briefly and add the remaining yogurt mixture on top. Cover with foil and leave to cool for 3 hours.
Then turn the terrine out of the mold, carefully cut into slices and arrange. Add fruit fillets if desired.