To a large bowl, prepare an ice bath by adding a heaping handful of ice cubes to a large bowl and topping it off with a few splashes of water. Set a slightly smaller bowl inside the larger bowl and place a sieve or strainer inside. Set the whole ice bath contraption aside.

Add the whole milk and pinch of salt to a medium saucepan. Turn the heat to medium and stir until the milk is hot to the touch. Turn off the heat and add the mint and submerge it in the milk; cover the pot and allow it to steep for 1 hour.

In a medium bowl, beat the egg yolks with the sugar; whisking them together until they turn a pale yellow, about 2 to 3 minutes. Remove the mint from the milk and discard. Bring the milk back until it's hot to the touch. Whisking the entire time, add about 1/4 cup of warm milk to the beaten egg yolks. Return the egg yolk and milk mixture back to the medium saucepan and place over medium low heat. Cook the mixture, stirring constantly, until the thermometer reads 170 to 175 degrees F and the custard appears thick and coats the back of a spoon.

Pour the custard through the sieve into the bowl. Stir in the heavy cream until completely incorporated. Keep mixing until the mixture is room temperature. When the custard has cooled down, stir in the spinach juice, about 2 tablespoons until it turns a pale yet vibrant green color. Place plastic wrap on the surface of the custard, which will prevent the surface from creating a skin, and transfer to the fridge for 4 to 5 hours, until very cold.

Mince up 3 to 4 leaves of fresh mint. When the custard is cold, churn the mixture into the bowl of your ice cream maker, according to the maker's instructions. At the very end of the ice cream churning, pour in the dark chocolate chunks and sprinkle in the minced mint. When the chocolate and mint are mixed and distributed throughout the ice cream, transfer it to a quart container and freeze until the ice cream is firm, about 4 to 8 hours.