Citrus and Yogurt Mousse

Soak gelatin in a bowl of cold water until softened, about 10 minutes. Rinse mandarin orange and lemon with hot water, then finely zest both. Mix zests together and set aside. Squeeze juice from orange and lemon halves. In a bowl, whisk yogurt with citrus juices and 2-3 tablespoons powdered sugar until smooth. Squeeze gelatin to remove water and melt in a saucepan over low heat. Stir in liqueur and 2-3 tablespoons yogurt cream, then whisk mixture back into the bowl of yogurt. Whip egg whites with remaining powdered sugar until stiff. Whip cream until stiff. Fold both egg whites and cream into yogurt mixture.

Divide mousse among four glasses, cover and refrigerate at least 2 hours.