In a heavy saucepan, the top of a double boiler or a metal bowl placed over water in a saucepan, stir together the egg whites and sugar from the recipe (at least 2 tablespoons sugar per white), water (1 teaspoon per white) and cream of tartar (1/8 teaspoon per each 2 whites). Cook over low heat or simmering water, beating constantly with a portable mixer at low speed, until the whites reach 160° F. Pour into a large bowl. Beat on high speed until the whites stand in soft peaks. Proceed with the recipe.
Note that you must use sugar to keep the whites from coagulating too rapidly. Test with a thermometer as there is no visual clue to doneness. If you use an unlined aluminum saucepan, eliminate the cream of tartar or the two will react and create an unattractive gray meringue.
Making an Italian meringue by adding hot sugar syrup to egg whites while beating them does not bring the egg whites to much above 125° F and is not recommended except for dishes that are further cooked. If, however, you bring the sugar syrup all the way to the hardball stage (250 to 266° F), the whites will reach a high enough temperature. You can use a sugar syrup at hardball stage for Divinity and similar recipes.
