1. Bring a medium pot of water to a boil. Add mint; return water to a boil. Using a slotted spoon, immediately plunge mint into an ice-water bath. Lift out mint; drain well. Reserve ice-water bath.

2. Bring milk to a simmer in a medium saucepan over medium heat. Add mint. Remove from heat. Let cool slightly.

3. Working in batches (so that blender is never more than halfway full), blend milk mixture until mint is pureed, at least 1 minute per batch. Pass through a fine sieve into a stainless-steel bowl set in reserved ice-water bath.

4. Stir simple syrup and corn syrup into milk-mint mixture. Let stand until cold, stirring occasionally. Refrigerate until very cold, at least 2 hours (or overnight).

5. Freeze in an ice cream maker according to manufacturer's instructions. Transfer to an airtight container. Freeze at least 1 hour. Before serving, let stand at room temperature to soften slightly.