1. Special equipment: a candy or instant-read thermometer, an ice cream maker
2. Bring cream, half-and-half, honey, and lavender just to a boil in a 2-quart heavy saucepan over moderate heat, stirring occasionally, then remove pan from heat.
3. Let steep, covered, 30 minutes.
4. Pour cream mixture through a fine-mesh sieve into a bowl and discard lavender.
5. Return mixture to cleaned saucepan and heat over moderate heat until hot.
6. Whisk together egg and salt in a large bowl, then add 1 cup hot cream mixture in a slow stream, whisking.
7. our into remaining hot cream mixture in saucepan and cook over moderately low heat, stirring constantly with a wooden spoon, until thick ehough to coat back of spoon and registers 170 to 175 degrees F on thermometer, about 5 minutes (do not let boil).
8. Pour custard through sieve into cleaned bowl and cool completely, stirring occasionally.
9. Chill, covered, until cold, at least 3 hours.
10. Freeze custard in ice cream maker.
11. Transfer ice cream to an airtight container and put in freezer to harden.