Whisk together the heavy cream, milk, sugar and fresh mint in a saucepan on the stove. Bring to a simmer over medium heat. Continue to whisk periodically to help dissolve the sugar. Do not bring to a boil. Once it simmers, turn off heat and if desired, lightly muddle the mint leaves to release even more mint oil. Cover and let the mint steep for at least an hour.
Strain mint. If it’s still warm, proceed to step three. If not, gently reheat on the stove just until warm. Again, don't boil. The mixture only needs to be warm.
Whisk the egg yolks and vanilla until pale, about three minutes. Temper about one-fourth cup of the warm cream mixture into the egg mixture, whisking constantly. Repeat this step a few times until you incorporate about half of the cream mixture.
Add tempered egg-cream mixture back to the pot. Whisk constantly over medium heat and bring back to a simmer. Again, do not boil. Cook until mixture thickens and covers the back of a wooden spoon. Turn off heat.
Pour into a large mixing bowl and allow to cool for a few minutes. Directly cover the top of the custard's surface with plastic wrap and refrigerate until cold, at least four hours to ensure proper churning, though I like to chill overnight to really make sure it's cold.
Pour custard into an ice cream maker and churn according to manufacturer’s directions. As the ice cream churns, melt the chopped chocolate with canola oil in the microwave, cooking in 15-second intervals and stirring until smooth. During the last few minutes of churning, slowly stream in the melted chocolate.
Pour the churned ice cream into an airtight container and freeze for several hours before serving. Enjoy!