01 - Place the peeled and sliced bananas into a blender along with the Greek yogurt, honey or maple syrup, and vanilla extract. Blend on high until the mixture is completely smooth and creamy, scraping down the sides as needed.
02 - Combine the dark chocolate and coconut oil in a microwave-safe bowl. Microwave in 20-second intervals, stirring between each, until fully melted and smooth. Alternatively, melt over a double boiler, stirring constantly.
03 - Pour half of the banana mixture into the popsicle molds, filling each one about halfway. Drizzle a spoonful of the melted chocolate over the banana layer in each mold, then use a skewer or thin knife to gently swirl the chocolate through the banana mixture for a marbled effect.
04 - Divide the remaining banana mixture among the molds, filling them to the top. Drizzle more melted chocolate over the surface and swirl again to create additional marbling throughout.
05 - Place popsicle sticks into the center of each mold, pressing gently so they stand upright. If desired, sprinkle the tops with chopped roasted nuts or mini chocolate chips before the mixture begins to set.
06 - Transfer the filled molds to the freezer and chill for a minimum of 4 hours, or until the popsicles are completely firm and frozen through.
07 - To remove the popsicles, briefly run the outside of each mold under warm water for 10 to 15 seconds. Gently pull the stick to release the popsicle. Serve immediately.