01 - Slice the peeled bananas and add them to a blender along with the Greek yogurt, honey or maple syrup, and vanilla extract. Blend on medium speed until the mixture is completely smooth and creamy, scraping down the sides as needed.
02 - Place the chopped dark chocolate and coconut oil in a microwave-safe bowl. Heat in 20-second intervals, stirring between each, until fully melted and glossy. Alternatively, melt over a double boiler set over simmering water, stirring gently until smooth.
03 - Pour half of the banana yogurt mixture into the popsicle molds, filling each about halfway. Drizzle a generous layer of the melted chocolate over the banana layer in each mold.
04 - Using a thin skewer or the tip of a knife, gently drag through the chocolate drizzle in a figure-eight motion to create a marbled effect. Be careful not to over-mix.
05 - Divide the remaining banana mixture among the molds, filling them to just below the rim. Drizzle more melted chocolate on top and repeat the swirling motion for additional marbling throughout.
06 - Insert a popsicle stick into the center of each mold, pressing gently until stable. If desired, sprinkle chopped roasted nuts or mini chocolate chips over the exposed surface before freezing.
07 - Transfer the filled molds to the freezer and chill for at least 4 hours, or until the popsicles are completely firm and set through to the center.
08 - To release the popsicles, briefly run the outside of each mold under warm water for 10 to 15 seconds. Gently pull the stick to remove. Serve immediately.