1. With the back of a large spoon, rub the fresh or thoroughly defrosted frozen strawberries through a fine sieve into a small mixing bowl. Stir into this puree the ½ cup of sugar, a little at a time.
2. Using a balloon-type wire whisk, beat the egg whites and salt vigorously in a large bowl (preferably of unlined copper) until the whites are stiff enough to form unwavering peaks when the beater is lifted out of the bowl.
3. With a gentle under-over cutting motion rather than a stirring motion, use a rubber spatula to fold first the strawberry puree and then the whipped cream into the egg whites.
4. Pour the strawberry snow into an attractive serving bowl, or individual dessert bowls, and decorate with the whole strawberries.
5. This dessert can be served at once, or it may be refrigerated for a few hours and served later in the day.
