Preheat the oven to 400 degrees F.
Combine milk, sugar and vanilla in a heavy, non-reactive saucepan
and bring to a boil. Meanwhile, sift
together cocoa and cornstarch. Remove boiled milk from heat. In a steady stream, whisk
dry ingredients into hot milk
. Stirring constantly, continue cooking until base is thickened and returns to a boil. Strain through a chinois
or fine mesh strainer
and chill in an ice-water bath.
Meanwhile, place the egg whites in the bowl of an electric mixer
fitted with the whisk attachment. Begin whipping the whites, gradually adding the sugar, until soft peaks are achieved. Gently fold the egg
whites into 1/4 cup of the base, and divide among the ramekins.
Tap the ramekins to release any large air pockets, and smooth the tops with a spatula
Transfer to the oven and bake for approximately 8 minutes, or until fully risen. Dust
with powdered sugar
and serve immediately.