Recipe adapted from All You.
Preheat oven to 375°. Spray an 8-inch square pan with cooking spray.
Whisk together flour, baking powder, and salt. Set aside.
Using an electric mixer, beat butter, oil, and sugar. Beat in eggs and egg white, 1 at a time, mixing well after each addition. Mix in vanilla.
In a separate bowl, mash bananas with milk. Set aside.
Gradually mix half of dry ingredients into butter mixture. Mix in bananas. Mix in remaining dry ingredients. Pour cake batter into prepared baking pan.
Bake 40-45 minutes, or until a toothpick inserted into center of cake comes out clean. Cool cake in pan on wire rack.
Using an electric mixer on medium speed, beat cream cheese and vanilla. Reduce speed and gradually add confectioners’ sugar.
Spread frosting on cake. Sprinkle with nuts.