This is a prime example of what we call a "Chef's Dessert." Most desserts start with the idea of something sweet and just keep building on sweetness. Thus, soufflés -- which can be wonderful and light -- often are just a mound of overpowering sweetness. Here, the idea that started the dessert was tanginess and then using only enough sugar to balance it. The trial and error that went on between chef and pastry chef required Chris Broberg, the pastry chef at Lespinasse, to run up the three stories to the chef's office about a hundred times before the dessert was just right. But pastry chefs can always use a little exercise to stay trim.
1 passion fruit
Approx. 2 cups sugar (don't worry, you bake the filled fruit on top of mounds of sugar, you don't include this all in the recipe)
Preheat the oven to 475° F. Slice about 1/2 inch from the top of the tangerine, then cut the lemon, lime and passion fruit in half. Scoop out the flesh of each fruit, taking care not to rip the citrus sieve and set the rinds aside. Press the fruit through the sieve, then sweeten the juice to taste (the juice should still be sour but have some sweetness to it).
Divide the sugar between six forms of a cupcake tin (each cup should be about one quarter full). Place a reserved rind in each sugar-filled cup. Spoon a tablespoon of sweetened citrus juice into each and set aside.
4 egg whites
2 egg yolks
4 tablespoons sugar
Put the egg whites and yolks in separate bowls. Put half the sugar in each bowl. Whisk the yolks until the thicken and have a satiny sheen. Whisk or beat the egg whites until they are firm enough to pull up into peaks but not so stiff that they stand up and remain that way. Fold half the egg whites into the yolks. When they are fully combined, fold in the rest. Spoon the soufflé batter into the fruit rinds. Place the soufflés in the lower third of the oven and bake until they rise and brown, 6-7 minutes. Serve immediately.