1. Peel and slice banana into about 1/2-inch slices. Place in freezer for 1 hour (it's optional, but it will be easier for you to dip them in chocolate).
2. Melt chocolate in a double boiler or simply by microwaving it in 30 second intervals (stir and check whether the chocolate is melted and smooth). Add melted coconut oil and mix well.
3. Dip banana piece in melted chocolate, letting excess chocolate drip off (I used a spoon and a fork for dipping). Place on a plate, previously covered with parchment paper (don't make my mistake, or you'll have to use a knife to remove the frozen banana bites). Sprinkle with chopped nuts. Repeat with the remaining banana pieces.
4. Freeze until firm, about 3 hours. Serve. Store in freezer in an airtight container or a freezer bag.