In a small bowl, whisk together 1/4 cup of the almond milk and cornstarch together until cornstarch is dissolved. Set aside.

In a pot (at least 4 qt.) set over medium to medium-high heat, pour in the remaining 1 1/3 cup almond milk, coconut milk, sugar, agave nectar, salt, cocoa powder, and espresso powder (if using). Whisk so that ingredients combine and sugar, cocoa powder, and espresso powder dissolve. Let mixture come to a low boil, then let cook for a few minutes, occasionally stirring. After 4-5 minutes, pour in the almond milk/cornstarch mixture and stir. Let mixture come back to a low boil and cook for an additional few minutes to thicken, stirring frequently.

Remove pot from heat and stir in peppermint extract. Pour into a large plastic bag (or two small ones) and seal. Set bag(s) in a bowl filled with ice water so that ice cream mixture cools quickly. I also placed the bowl in the refrigerator to help speed the process along.

After a few hours or whenever mixture is chilled, pour into ice cream maker and prepare according to your ice cream maker's directions. Just before ice cream is finished, add chocolate chunks. Ice cream will be soft at this point, like soft-serve. Transfer ice cream to a container and freeze.