Peach Purée
8 to 10 ripe peaches
1/2 cup sugar
juice of 1 lemon
Blanch peaches for 2 minutes. Remove from boiling water and plunge into ice water. Peel, cut in half, and remove pits. Place peaches in a saucepan, barely cover with water, and add sugar and lemon juice. Simmer over medium heat until sugar dissolves and peaches are somewhat soft but not mushy, about 10 minutes. Drain and let cool, then transfer to a food processor and pulse only until roughly puréed (large pieces of peach should remain intact). Cover and refrigerate.
Ice Cream
4 cups whole milk
4 cups heavy cream
15 egg yolks
1 cup sugar
1 tablespoon vanilla extract
Pour milk and cream into a large saucepan and scald (heat until tiny bubbles form around edge of pan). Set aside. Meanwhile, in a mixing bowl, beat yolks and sugar with a metal spoon until sugar dissolves (do not use a whisk, to avoid adding excess air to mixture). Gradually pour half the milk mixture into the bowl with the egg mixture, stir well, and pour back into the saucepan with the other half of the milk mixture. Cook this custard over medium heat, stirring constantly, until slightly thickened (it should coat the back of a wooden spoon). Do not allow to boil or yolks will curdle. Remove from heat, add vanilla, put through a fine metal strainer, and freeze in the container of an ice-cream maker. When frozen, transfer the custard (which should be semi-soft) and the peach purée to a bowl, alternating layers of each (the number of layers does not matter). Lightly mix with a knife or spoon (swirls and bits of peach should be visible). Cover and chill in the freezer of your refrigerator for at least two hours.
