PREHEAT oven to 350°F. Microwave chocolate and oil in glass measuring cup on HIGH 1 to 2 min. or until completely melted. Stir in cocoa powder; let stand at least 5 min.
BEAT egg whites and sugar in medium bowl with electric mixer on high speed 3 min. or until tripled in volume. Reduce speed to medium low; blend in melted chocolate mixture until well combined. Spoon batter into 6 paper-lined medium muffin cups. (Muffin cups can be almost full.)
BAKE 18 min. or until puffed and center is set. Remove from oven; let stand in pan 5 min. Serve warm with whipped topping.