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 with no lumps remaining.
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 set over gently simmering water, stirring constantly.
03 - Pour half of the banana mixture into the popsicle molds, filling each one about halfway. Drizzle a generous layer of the melted chocolate over the banana layer in each mold. Use a skewer or small knife to gently swirl the chocolate into the banana base 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 with a skewer to create additional marbling throughout.
05 - Insert a popsicle stick into the center of each mold, pressing down gently to anchor it. If desired, sprinkle the tops with chopped roasted nuts or mini chocolate chips while the surface is still soft.
06 - Place the filled molds in the freezer on a level surface. Freeze for a minimum of 4 hours, or until the popsicles are completely firm and set through to the center.
07 - To remove the popsicles from the molds, briefly run warm water over the outside of each mold for a few seconds. Gently pull the popsicle upward by the stick. Serve immediately.