01 - Combine milk, 1 cup cream, sugar, and salt in a medium saucepan. Heat over medium heat until steaming but not boiling. Remove from heat, add mint leaves, cover, and steep for 1 hour to infuse flavor.
02 - Strain out mint leaves, pressing firmly to extract maximum flavor. Return milk mixture to saucepan and reheat until warm if needed.
03 - Whisk egg yolks in a separate bowl. Gradually pour warm milk mixture into yolks while whisking constantly to prevent curdling. Return combined mixture to saucepan.
04 - Cook over medium-low heat, stirring constantly, until mixture thickens and coats the back of a spoon (170-175°F). Do not boil to prevent scrambling.
05 - Remove from heat and stir in remaining 1 cup cream. Add vanilla extract and green food coloring if desired.
06 - Pour custard through fine-mesh sieve into clean bowl. Cool to room temperature, then cover and refrigerate until thoroughly chilled, at least 4 hours or overnight.
07 - Churn chilled custard in ice cream maker according to manufacturer's instructions. During final minutes of churning, add chopped chocolate and mix until evenly distributed.
08 - Transfer ice cream to airtight container and freeze until firm, at least 2 hours. Let sit at room temperature for 5 minutes before scooping for optimal texture.