Place the sugar in a large mixing bowl, and add the sugar.

Step 1
Whisk until smooth.

Step 2
Add the baking powder and cornstarch and whisk again.

Step 3
Add the yogurt and whisk until all the ingredients are well combined.

Step 4
In another clean bowl, beat the egg whites until stiff peaks form.

Step 5
Fold the whipped egg whites into the batter.

Step 6
Add the chocolate chips and mix gently.

Step 7
Pour the batter into an 8-inch cake pan lined with parchment paper. Bake at 170°C/350°F for 1 hour.

Step 8
Dust with powdered sugar.

Step 9
Serve and enjoy!