Start by preparing your baking pan: Line an 8x8 inch square baking dish with parchment paper, ensuring that the edges extend beyond the pan sides for easy lifting later. Set this aside.
In a medium-sized saucepan, combine the creamy peanut butter and sweetened condensed milk. Heat them gently over low heat, stirring constantly for about 3-4 minutes until the mixture is smooth and fully blended together.
Once the peanut butter mix is homogeneous, introduce the semisweet chocolate chips and the cocoa powder into the saucepan. Keep stirring until the chocolate chips are completely melted and the mixture transforms into a rich, creamy consistency.
Remove the saucepan from heat, and stir in the vanilla extract along with a pinch of salt, ensuring everything is well incorporated.
Carefully pour the luscious fudge mixture into the prepared baking pan, using a spatula to evenly smooth out the surface.
If you wish to add a crunchy element, sprinkle chopped nuts over the fudge and gently press them in to ensure they adhere to the surface.
Place the fudge in the refrigerator for a minimum of 2 hours, allowing it to firm up and set completely.
After chilling, utilize the overhanging edges of the parchment paper to lift the fudge out of the pan. Cut it into squares for serving.
Notes
For an elegant touch, drizzle some melted chocolate over the top and garnish with whole roasted peanuts or cocoa powder.