Peel the bananas and slice them into 1/2-inch thick rounds.
Line a baking sheet with parchment paper.
Spread a small amount of peanut butter on half of the banana slices and top with the remaining banana slices to create little sandwiches.
In a microwave-safe bowl, combine the dark chocolate chips and coconut oil. Microwave in 30-second intervals, stirring in between, until melted and smooth.
Dip each banana sandwich into the melted chocolate, ensuring it is fully coated. Use a fork to lift it out and let any excess chocolate drip off.
Place the chocolate-covered banana bites back on the parchment-lined baking sheet. If desired, sprinkle with chopped nuts or a pinch of sea salt before the chocolate sets.
Freeze the banana bites for at least 2 hours or until solid.
Once frozen, transfer the bites to an airtight container and store in the freezer for up to 2 months.