Add whipping cream to pan and heat to boiling, stirring occasionally. Boil uncovered 6 minutes, stirring occasionally, until sauce is thickened and reduced to about 1/2 cup. Remove from heat and add lemon peel. Beat in butter, 1 piece at a time, with wire whisk, adding the next piece only after the first has been completely beaten in and melted. When all of the butter has been beaten in, add 1/4 teaspoon salt and the white pepper. Cover to keep warm.