Peel your bananas and slice them into rounds about a quarter-inch thick. Try to keep the slices roughly the same size so they freeze at the same rate. Lay them out in a single layer on your parchment-lined baking sheet.
Spoon a small dab of peanut butter onto half of your banana slices. Top each one with a second slice to form a little sandwich, pressing gently so the peanut butter holds everything together.
Place the tray in the freezer for about an hour, or until the banana sandwiches feel firm to the touch. This step keeps the bananas from turning mushy once you dip them, and it makes handling them so much easier.
While the bananas are freezing, combine your chocolate chips and coconut oil in a microwave-safe bowl. Heat in 30-second bursts, stirring in between, until the mixture turns smooth and glossy.
Remove the frozen banana bites from the freezer and use two forks to dip each one into the melted chocolate. Let the excess drip off, then set the bites back onto the parchment paper. Sprinkle with chopped peanuts or sea salt right away, before the chocolate sets.
Return the tray to the freezer for another hour, or until the chocolate coating is completely hardened. Once set, transfer the bites to a container for storage, or serve a few straight away while they're still ice cold.