2 1/2 cups plain Greek yogurt
1/2 cup granulated sugar
1 teaspoon vanilla extract
Pinch kosher salt
About 3 tablespoons cocoa powder
In a medium bowl, whisk together the yogurt, sugar, vanilla, and salt. Use a baster to apply one small layer of this mixture to the bottom of your popsicle molds. Tap the bottoms of the molds on your work surface to even out the layers.
Whisk 1 teaspoon of cocoa powder into the yogurt mixture and then use the baster to apply another layer into your molds. Tap the bottoms again to even it out. Whisk another teaspoon of cocoa powder into the yogurt mixture and repeat this process.
Continue adding layers and whisking in teaspoons of the cocoa powder to make darker and darker layers until you've filled up your molds. Stick in your popsicle sticks and freeze for about 2 hours, or until frozen all the way through.