01 - Combine heavy cream, whole milk, and fresh mint leaves in a medium saucepan. Heat over medium until just simmering, then remove from heat. Cover and steep for 30 minutes.
02 - Strain the mixture through a fine-mesh sieve, pressing to extract flavor. Discard mint leaves and return the infused cream to the saucepan.
03 - In a medium bowl, whisk egg yolks and granulated sugar until pale and slightly thickened.
04 - Gradually pour the warm cream mixture into the egg yolks while whisking constantly to temper.
05 - Return the combined mixture to the saucepan. Cook over low heat, stirring constantly with a wooden spoon, until custard thickens and coats the back of the spoon (77–80°C or 170–175°F), about 5–7 minutes. Avoid boiling.
06 - Remove from heat and stir in peppermint extract and optional green food coloring.
07 - Transfer custard to a clean bowl. Cool to room temperature, cover, and refrigerate until thoroughly chilled, at least 4 hours or overnight.
08 - Churn the chilled custard in an ice cream maker according to manufacturer’s instructions.
09 - Fold mini chocolate chips into the ice cream at the end of churning, if using.
10 - Transfer to a lidded container and freeze for at least 2 hours before serving.