In a small sauce pan, beat the egg well and add zest, juice, sugar and 1/3 c. half and half. Bring to a bare simmer over medium heat, whisking constantly. Remove from heat, strain, and refrigerate until cold. Add the remaining half and half and freeze in ice cream maker,
Notes
This made two nice servings of ice cream. Variations might include swapping almond extract for vanilla, or milk or plain yogurt for half and half.