How to Make It
In a large metal bowl, using an electric mixer, beat 1 cup of the sugar with the eggs, lemon juice and lemon zest. Set the bowl over a saucepan of simmering water and beat the mixture until it is thick enough to leave a trail when the whisk is lifted, about 15 minutes. Let cool slightly, then strain into a blender. Gradually add the butter, blending at high speed until the cream is light and perfectly smooth, about 5 minutes. Scrape down the container as needed. Transfer the cream to a bowl, cover and refrigerate for up to 2 days.
In a small saucepan, sprinkle the gelatin over the water and let stand for 5 minutes. Cook over low heat, stirring, until the gelatin dissolves. In a large bowl, combine the gelatin mixture with 2 tablespoons of the yogurt and the remaining 1/3 cup of sugar. Mix in the remaining yogurt and the cold lemon cream. Lightly whip the heavy cream and fold it into the lemon cream. Refrigerate, covered, for at least 1 hour and up to 1 day.
Melt the chocolate in a medium metal bowl set over a saucepan of simmering water, stirring until smooth. Line 2 baking sheets with parchment paper. Using an offset spatula, spread half of the chocolate evenly over each sheet. Chill until almost set, 5 to 10 minutes. Using a 4-inch round biscuit cutter, stamp out 10 rounds. Return the baking sheets to the refrigerator and chill again to firm up the chocolate, at least 15 minutes.
Combine all of the ingredients in a blender; blend until pureed. Transfer to a bowl, cover and refrigerate for up to 1 hour.
In a bowl, combine the pineapple, apples and corn and toss to mix.
For each dessert, set a 4-inch dessert ring or empty 12-ounce tuna fish can with the ends removed in the center of a soup or dessert plate and pack it halfway with salad. Fill the ring to the top with the lemon cream. Lift off the ring. Carefully peel a white chocolate round off the parchment paper and set it on top. Spoon some of the coulis around the plate and garnish with the red currants. Serve immediately.