In a shallow pan, combine milk, sugar, lemon juice, and lemon peel, stirring until sugar dissolves.
Place in freezer until cream is frozen.
Cut remaining lemons in half lengthwise; remove pulp and refrigerate for another use.
Place lemon shells in freezer.
Transfer frozen cream to work bowl of food processor or blender and process until smooth.
Return cream to freezer until partially frozen; fill lemon shells with partially frozen cream and refreeze until ready to serve.