Lemon Sauce

Combine the sugar and slivered lemon peel in a food processor and twirl until the lemon peel is grated fine. Add the cornstarch or arrowroot and salt and process a second or two more. Add the water and process another 20 seconds. Pour the mixture into an enamel or stainless steel very heavy saucepan. Boil over medium heat until the sauce is clear and thick enough to coat a wooden spoon, about 5 to 6 minutes. Remove the pan from the heat and allow sauce to cool down slightly. Whisk the egg yolks and lemon into the sauce. Return it to the stove and cook over medium heat while continuing to whisk until the yolks have thickened the sauce a little bit, about 3 minutes. Add the butter to the sauce. Blend it in by whisking in 1 direction. Taste and add more lemon if desired. Makes about 1-1/4 cups sauce.