If you have an unlined copper bowl, you can use it for whipping the egg whites, omitting the cream of tartar. Cooks use cream of tartar to help stabilize beaten egg whites, but copper interacts chemically with egg whites to yield much the same result. If whipping to soft peaks, the peaks should droop when the beaters are lifted; if whipping to stiff peaks, they should stand upright. To make whipped cream, in a large metal bowl, combine 1 cup well-chilled heavy cream, 1 tsp. vanilla extract and 2 Tbs. confectioners' sugar. Using an electric mixer on medium-high speed, beat until soft peaks form.