To make the dark chocolate layer, in a medium mixing bowl, combine 2 cups of greek yogurt, the dark cocoa powder, ½ cup pure maple syrup, and 1 ½ teaspoon peppermint extract. Stir to combine.
Spread the chocolate mixture out onto a rimmed baking sheet that has been lined with parchment paper.
Transfer to freezer, and freeze for 30 minutes.
To make the white layer, in a medium mixing bowl, combine the remaining 2 cups plain greek yogurt, remaining ¼ cup pure maple syrup, 1 teaspoon peppermint extract, abd ½ teaspoon vanilla extract. Stir to combine.
Spread the white layer over the frozen chocolate layer, and return the baking sheet to the freezer.
Freeze for 3-4 hours, or until solid. Freezing overnight works well, too.
When completely frozen, break into bite-size portions using your hands.
Store in the freezer in an air-tight container for up to 2 months.