Steps
1. In a saucepan, melt butter and chocolate over low heat. 2. In a separate bowl, mash the banana. 3. Whisk egg into the mashed banana. 4. Slowly pour in milk while stirring. 5. Gradually add the melted chocolate mixture. 6. Cook over medium heat until thickened, stirring constantly. 7. Remove from heat and let it cool. 8. Serve chilled.