Preheat the oven to 325°F (170°C). Tear off a large piece of parchment paper and push it down into a 7-inch (18 cm) round springform pan or cake pan so that the paper sticks up at least an inch (2.5cm) all the way around. Flatten the creases in the paper as best you can. To get the best rise and fluffiest cake, it's important to use this small size of pan. If you use a larger pan (no bigger than 8-inch/20cm) the yogurt cake will be flatter and not quite as fluffy, but still taste as good.
Using a stand mixer or hand mixer, beat the egg whites with the salt until they are stiff. Remove them to a separate bowl.
Add the egg yolks to the mixing bowl along with the sugar. Beat them together until they are pale yellow and fluffy. This will take 3 to 4 minutes on high speed. Beat in the yogurt and vanilla. Then add the starch and continue beating until it is mixed in.
Fold the beaten egg whites into the yolk/yogurt mixture ⅓ at a time. Gently fold in until only pea-sized pockets of beaten whites remain. Don't over-fold. Pour the batter into the parchment-lined baking pan. Bang it on the counter a few times to get any air bubbles to rise.
Bake for 40 to 50 minutes, until the center no longer feels liquid when gently pressed with your finger, and the edges are nicely browned.
Allow the cake to cool in the pan, then lift it out using the paper and gently peel off the parchment paper from the cake. Dust with icing sugar and serve with whipped cream and fresh fruit.
Serves 6 to 8.
Notes
If I just have cornstarch, that works great - it is the starch I use most often when I make this cake. But if you happen to have either some potato starch or arrowroot starch and substitute it for some of the cornstarch (even using 2 tablespoons each of all three starches), I find the texture of the cake seems to be even a bit more silky. I discovered this one day when I had only a bit of cornstarch left in the jar.*I always use organic cornstarch, to ensure it is not made from genetically modified corn.