Preheat the oven to 350℉. Spray an 8x8-inch pan with nonstick spray.
In a large bowl, use an electric mixer to beat together the butter and sugar until flight and fluffy- about 2 minutes. Beat in the egg. Add in the banana and milk, and continue to mix until combined.
In a large bowl, use an electric mixer to beat together the butter and sugar until flight and fluffy- about 2 minutes. Beat in the egg. Add in the banana and milk, and continue to mix until combined.
Scrape the batter into the prepared pan and smooth the top to even it out. Sprinkle ¼ cup of chocolate chips on top of the batter.
Bake 30 to 35 minutes, or until a toothpick tests clean when inserted into the cake. Let the cake cool completely before cutting.