01 - Place the peeled and sliced bananas into 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 - Combine the dark chocolate and coconut oil in a microwave-safe bowl. Heat 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 up. Drizzle a generous layer of the melted chocolate over the banana layer in each mold.
04 - Using a 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 overmix, as you want distinct ribbons of chocolate running through the base.
05 - Divide the remaining banana mixture among the molds, filling them to just below the rim. Drizzle with more melted chocolate and repeat the swirling technique for a consistent marbled appearance throughout.
06 - 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, pressing them lightly so they adhere.
07 - Transfer the filled molds to the freezer and freeze for a minimum of 4 hours, or until the popsicles are completely firm and set through to the center.
08 - To release the popsicles, briefly run warm water over the outside of each mold for 10 to 15 seconds. Gently pull the stick to slide the popsicle free. Serve immediately.