Beat egg whites thoroughly, close to 10 minutes. Add sugar, tablespoon by tablespoon at first, while continuing the beating of the egg whites. Amount of sugar can be increased gradually as the egg whites take it up. Be sure all the sugar is absorbed.

Continue beating and add vinegar, vanilla and baking powder.

For muffin tins, butter well, place in oven for a moment or two and then in refrigerator until ready to use.

Spoon mixture into tins and bake in slow oven, 250 to 300 degrees for 50 to 60 minutes.