Adjust oven rack to middle position and heat oven to 350 degrees. Use cake goop to prepare an 8-inch square baking pan. Whisk flour, salt, and baking soda together in bowl.
Using stand mixer fitted with paddle, beat butter and sugar on medium-high speed until pale and fluffy, about 3 minutes. Add eggs, one at a time, and beat until combined. Add bananas and vanilla and beat until incorporated.
Reduce speed to low and add flour mixture in 3 additions, alternating with milk in 2 additions, scraping down bowl as needed. Using rubber spatula, stir in ½ cup chocolate chips. Transfer batter to prepared pan and smooth top with rubber spatula. Sprinkle remaining ½ cup chocolate chips evenly over top. Bake until toothpick inserted in center comes out clean, 45 to 50 minutes, rotating pan halfway through baking.
Let cake cool completely in pan on wire rack. Serve. (Cooled cake can be wrapped in plastic wrap and stored at room temperature for up to 2 days.)