Preheat your oven to 350°F (175°C).
Line the baking pan with parchment paper, leaving some overhang for easy removal later.
In a food processor or blender, puree the ripe bananas until smooth. Measure out ⅔ cup and set aside.
In a saucepan over low heat, combine the chocolate chips, unsweetened cocoa powder, and sweetened condensed milk. Stir continuously until melted and well combined.
Remove from heat and mix in the pureed bananas, chopped nuts (if using), vanilla extract, and a pinch of salt. Stir until everything is well incorporated.
Pour the fudge mixture into the prepared baking pan and spread it evenly using a rubber spatula.
Bake for 25 minutes, or until the fudge is set and slightly puffed.
Allow the fudge to cool in the pan for about 10 minutes, then lift it out using the parchment paper. Let it cool completely on a wire rack before cutting into squares.