Peel the bananas and slice them into 1-inch thick rounds. Arrange the banana slices on a parchment-lined baking sheet.
Using a small spoon, spread about 1 teaspoon of peanut butter on half of the banana slices. Top with the remaining banana slices to create little sandwiches.
Place the baking sheet in the freezer for about 1 hour, or until the banana sandwiches are firm.
In a microwave-safe bowl, combine the dark chocolate chips and coconut oil. Microwave in 30-second intervals, stirring in between, until the chocolate is completely melted and smooth.
Remove the banana sandwiches from the freezer. Dip each sandwich into the melted chocolate, ensuring they are fully coated. Use a fork to lift them out, allowing excess chocolate to drip off.
Place the chocolate-coated sandwiches back on the parchment-lined baking sheet. Sprinkle with chopped roasted peanuts and a pinch of sea salt before the chocolate sets.
Return the baking sheet to the freezer for another 30 minutes to allow the chocolate to harden completely.