Combine half and half and lemon peel in heavy medium saucepan and bring to boil slowly over very low heat.
Remove from heat, cover and set aside 10 minutes.
Beat sugar with yolks in large bowl until pale yellow and mixture forms slowly dissolving ribbon when beaters are lifted.
Strain half and half, discarding lemon peel.
Slowly pour hot half and half over yolk mixture in thin steady stream, stirring constantly.
Return mixture to saucepan.
Place over low heat and cook, whisking constantly, until mixture is thick enough to coat back of wooden spoon; do not boil or mixture will curdle (if curdling occurs, immediately transfer mixture to blender and mix at high speed until smooth).
Transfer to bowl.
Set over bowl of ice water.
Cool completely, covering with waxed paper to prevent skin from forming on surface.
Stir lemon juice and ginger into cooled yolk mixture.
Refrigerate until thoroughly chilled, at least 1 hour.