Slice bananas into1/3-inch thick slices and arrange in one layer on baking sheet lined with parchment paper.Add a dollop (1/2 to 1 teaspoon) of nut butter to half the banana slices, then sandwich with a plain banana slice.Place the baking sheet into the freezer for 20-30 minutes.Towards the end of that time, combine chocolate chips and coconut oil in a microwave-safe bowl. Microwave at 50% power with 30 second bursts stirring between each one until melted and smooth.Or use double boiler method - (pot of boiling water with a bowl resting on top) melt the chocolate chips, condensed milk and coconut oil together.Once bananas are chilled, use two forks to dip banana bites in the melted chocolate.Place on parchment paper lined baking sheet once more, sprinkle with sea salt, then chill until hardened.Keep in refrigerator or up to 1 week or freezer for up to 3 months.