Step #1 leaves are measured by "hardpacking:" press down in the measuring c with your fingers In a heavy 2-quart saucepan or double boiler over medium-low heat, milk, stir & heat the cream, & sugar until the sugar dissolves.
Step #2 Do not boil.
Step #3 In a small bowl, whisk the egg yolks lightly.
Step #4 While whisking, pour 1 c of the hot cream mixture into the bowl, then pour the egg mixture back into the saucepan & place over medium-low heat.
Step #5 Stir constantly with a wooden spoon (don't let the mixture boil; it could curdle) for about 8 mins, or until it begins to thicken & coats the spoon.
Step #6 To test for doneness, dip a metal spoon into the mixture & run your finger across the back.
Step #7 The custard is done when your finger leaves a clear, clean trail.
Step #8 A candy thermometer should read 175-180 degrees F.
Step #9 Remove the pan from the heat & stir in the the vanilla.
Step #10 stir in the the lemon peel, lemon juice, & hard-packed lemon herbs into the hot ice-cream base.
Step #11 Cover & chill in the refrigerator for at least 1 hr (the longer it is put in the fridged, the stronger the flavor will be).
Step #12 Strain the mixture & add the sliced lemon balm leaves for color.
Step #13 Pour the mixture into an ice-cream maker & freeze according to the manufacturer's instructions.