Combine 1 ½ cups whole milk, heavy cream, and fresh mint in a food storage container and place in refrigerator to steep overnight (or at least 8 hours.)
When ready to continue making the ice cream, combine additional two tablespoons of whole milk and corn starch in a small bowl. Whisk together to make a slurry. Set aside.
Next, combine the mascarpone and salt in a large bowl (preferably with a lid). Stir or whisk until salt is incorporated into mascarpone. Set aside.
Remove steeped milk mixture from refrigerator and add to a large saucepan (at least 4 quarts) along with sugar, corn syrup and vanilla. Bring to a boil and continue to boil for 4 minutes.
Remove saucepan from heat and slowly stir in corn starch mixture. Place back on heat and bring to a boil once again. Stir continuously for one minute, until mixture begins to thicken.
Slowly pour this mixture through a strainer into the bowl with the mascarpone. The goal is to remove most of the mint leaves. Some small ones may sneak through, but that’s okay. Stir the milk mixture into the mascarpone until well-combined. Cover with lid (or plastic wrap if you don’t have a bowl with a lid) and place in refrigerator for at least a couple of hours, or until the mixture is cool.
Once cool, add mixture to ice cream maker with the chopped dark chocolate pieces and churn according to manufacturer’s directions. My ice cream mixture appeared to stop churning at one point, but upon touching it I realized it was still a bit too soft, so I simply placed the ice cream canister in the freezer for a bit until the ice cream was the consistency I was looking for.
Transfer the ice cream to a covered container and store in the freezer. Best enjoyed within a week for freshness!