Chocolate Banana Upside Down Cake

Name: Chocolate Banana Upside Down Cake
Prep time: 15 min
Cook time: 25 min
Total time: 40 min
Cuisine: American
Ingredients: 2 to 3 bananas; 1 1/2 Tbsp of butter (20g); 1 to 2 Tbsp of brown sugar (14 to 28g); 1 egg; 1/4 to 1/3 cup of white granulated sugar (50 to 66g); 1 tsp of vanilla extract (5g); 3 Tbsp of cooking oil (45g); 1/3 cup plus 2 Tbsp of milk (105g); 1 cup of all-purpose or cake flour (120g); 3 Tbsp of cocoa powder (40g); 2 tsp of baking powder (10g); 1/4 tsp of salt (1g)