In a mixing bowl whisk a scant 1 cup of the Greek yogurt mixture with 3 Tbsp cocoa powder until well blended. Stir in 1/2 Tbsp milk at a time to thin as needed (you don't want a thick mixture). Pour into a quart size resealable bag, seal bag and cut a tiny tip from corner then pour mixture into an even layer among popsicle molds (I use these here
) filling about 1/3 full, being careful not to run down the sides (you can clean edges with a damp paper towel or q-tip as needed). Freeze 5 - 10 minutes (just to help set the top layer a bit).