Prepare an ice-water bath and set aside. Boilmint in a water until bright green for about 1 minute. Drain using a slotted spoon then transfer to ice-water bath. When cool, squeeze out excess water. Reserve ice-water bath.
Puree mint and milk in a blender. You may leave some chunks of spearmint if you prefer. Transfer to a saucepan, add cream, and bring to a simmer over medium heat.
Whisk together sugar and eggs in a medium bowl.
Gradually whisk part of the cream mixture into the egg mixture. Pour egg-cream mixture into the saucepan to the remaining cream mixture. Set over medium heat. Stir constantly with a wooden spoon, until thick enough to coat the back of the spoon.
Strain through a fine sieve. Use a heatproof bowl. Press on mint and extract liquid. Set bowl in ice-water bath. Let cool completely by stirring occasionally. Freeze in an ice cream maker according to manufacturer's instructions. Transfer to an airtight container, and freeze until firm, about 4 hours (or up to 1 week).